Hypophosphatasia (HPP) is the inborn-error-of-metabolism from deactivating mutation(s) of ALPL, the gene that encodes the cell surface "tissue-nonspecific" isoenzyme of alkaline phosphatase (TNSALP). HPP's "biochemical signature" comprises low serum alkaline phosphatase activity together with elevated plasma levels of the TNSALP natural substrates phosphoethanolamine (PEA), pyridoxal 5'-phosphate (PLP), and inorganic pyrophosphate (PPi). Excess extracellular PPi (ePPi) inhibits mineralization and affected children prematurely shed deciduous teeth and often suffer weakness and rickets. Yet, HPP severity is greatest among all dento-osseous disorders and not fully explained by autosomal dominant versus autosomal recessive inheritance involving >470 ALPL mutations. Discordance of HPP phenotype sometimes manifests even among full siblings sharing an identical ALPL genotype. Herein, a girl's markedly discordant HPP featured at presentation life-threatening hypercalcemia, failure-to-thrive, and renal compromise. Subsequent pseudotumor cerebri syndrome caused blindness, and then craniosynostosis required cranial vault reconstruction. However, she was not deformed, had moderate hypophosphatasemia, normal plasma PLP level, and mild radiographic features of HPP rickets. Elevated plasma N-terminal parathyroid hormone-related protein (PTHrP) suggested malignancy, but corrected after kidney transplantation. HPP was diagnosed when whole exome sequencing revealed heterozygous ALPL c.1034C>T, p.A345V reported in mild pediatric HPP and transmitted by her mother who considered herself well. Genes conditioning ePPi formation and underlying other skeletal diseases were intact. Hypercalcemia, unresponsive to bone antiresorptive drugs, corrected promptly with asfotase alfa TNSALP supplementation therapy. Her markedly discordant findings highlight genotype/phenotype plasticity for pediatric HPP, and her clinical course importance for early diagnosis.

Hypophosphatasia (HPP) is a hereditary disorder characterized by impaired bone mineralization caused by decreased tissue-nonspecific alkaline phosphatase (TNSALP) activity. Specifically, HPP is caused by a loss-of-function variant in the ALPL gene encoding TNSALP. Although genotype-phenotype correlations have been described, phenotypic differences have been reported in patients with the same variants, even within families. The proband, a girl, was suspected to have in utero fractures of the long bones, suggestive of osteogenesis imperfecta. No respiratory impairment was observed after birth; however, the patient's serum alkaline phosphatase level was low. In addition, the patient's perinatal findings were consistent with those of perinatal benign HPP, although the bone symptoms subsequently worsened. The patient's brother, initially suspected to have odonto-HPP due to the premature loss of primary teeth, later developed compression fractures and extraosseous symptoms. Both patients had the same ALPL variants, c. 572A>G(;)1559del, p. Glu191Gly(;)Leu520ArgfsTer86; however, the severity of their conditions differed. Patients with HPP with identical genotypes in the same family may have varying severity levels of HPP. In this case report, both patients received enzyme replacement therapy (ERT), which improved the clinical symptoms. Therefore, for perinatal benign HPP, ERT should be considered if bone symptoms worsen. In addition, odonto-HPP should be closely monitored, and ERT should be considered if bone and extraosseous symptoms arise.

The use of asfotase alfa, a bone-targeted recombinant alkaline phosphatase (ALP) enzyme, for the treatment of adult-onset hypophosphatasia (HPP) remains controversial, particularly in patients without evident bone abnormalities. We report the case of a 41-year-old woman with a history of Graves' disease, who presented with progressive joint pain and severe fatigue. Despite the absence of bone lesions, the patient was diagnosed with HPP based on persistently low alkaline phosphatase levels, family history, and a novel heterozygous ALPL variant (p.Ala205Thr). Functional analysis revealed a dominant-negative effect for this variant. Her symptoms significantly interfered with her daily activities owing to uncontrolled pain and loss of motor function and were so exacerbated that high doses of acetaminophen and NSAIDs were ineffective. Treatment with asfotase alfa was initiated based on multidisciplinary team consensus. Within 3 months of treatment initiation, her pain improved significantly, as indicated by reduced scores on the visual analog scale from 6.6 to 0.9, and elimination of the need for analgesics. Additionally, her grip strength increased, and her urinary phosphoethanolamine levels and serum pyridoxal 5'-phosphate/pyridoxal ratio decreased from 90.4 to 57.8 μmol/g·creatinine and from 4.6 to 0.4, respectively. These improvements have been maintained for more than 2 years. This case highlights the potential of asfotase alfa in effectively alleviating symptoms in patients with adult-onset HPP without bone lesions, emphasizing the importance of patient selection and outcome monitoring. We also discuss the key considerations for future treatment, supported by a literature review of asfotase alfa in adult patients with HPP.

Asfotase alfa (AA) is an FDA-approved enzyme replacement therapy for hypophosphatasia (HPP). Limited real-world data on its adverse events (AEs) exist. This study evaluates AA-related AEs using the U.S. FDA's Adverse Event Reporting System (FAERS) database.

Reports for AA were extracted from FAERS and analyzed per FDA guidelines. AEs were categorized using MedDRA version 26.1. Disproportionality analysis was conducted using the reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian confidence propagation neural network (BCPNN), and empirical Bayes geometric mean (EBGM) algorithms. Time-to-onset (TTO) was calculated, with a Weibull shape parameter test to assess risk over time.

Out of 13,702,373 reports, 5,040 AA-related AEs were identified, with 198 significant preferred terms (PTs). Common AEs included injection site reactions and pain, with additional PTs for ear/labyrinth disorders and infections. The median onset for 234 AEs with reported times was 170 days (IQR 18-390 days). No significant differences in AEs were found across gender or age groups.

Most AEs align with known data, but newly identified ear/labyrinth disorders and infections require further investigation to enhance AA's safety profile.

Hypophosphatasia (HPP) is a rare metabolic disease caused by autosomal dominant or recessive inheritance of ALPL variants resulting in low alkaline phosphatase activity. The objective of this analysis was to compare HPP disease burden between patients with non-life-threatening disease in the Global HPP Registry who have one ALPL variant versus two or more ALPL variants.

Patients were included if they had one or more ALPL variants identified through genetic testing and first HPP manifestations after 6 months of age. Assessments included history of HPP manifestations, Brief Pain Inventory-Short Form (BPI-SF), Health Assessment Questionnaire-Disability Index (HAQ-DI), 6-Min Walk Test (6MWT), Paediatric Quality of Life Inventory (PedsQL) and 36-Item Short-Form Survey V.2 (SF-36v2).

Of 685 included patients, 568 (82.9%) had one ALPL variant, 116 (16.9%) had two variants, and one (0.1%) had three variants. Patients with two or more ALPL variants had higher proportions of skeletal (52.1% vs 32.6%), dental (73.5% vs 56.0%), muscular (36.8% vs 23.6%) and neurological (22.2% vs 8.8%) manifestations at last assessment. BPI-SF, HAQ-DI, PedsQL and SF-36v2 scores were similar between groups. Distances walked on the 6MWT were similar between groups for children. Distance walked was lower among adults with two or more variants (293 m (n=8)) than adults with one variant (466 m (n=103)), although the former group was very small.

HPP disease burden is high in patients with HPP, regardless of ALPL variant number. While prevalence of HPP-specific manifestations was higher in patients with two or more variants than those with one variant, patient-reported outcomes were similar between groups.

NCT02306720; EUPAS13514.

Hypophosphatasia (HPP) is a rare, dento-osseous disorder caused by impaired activity of tissue non-specific alkaline phosphatase (TNSALP), a key enzyme in tissue mineralization. This review provides a clinical perspective on the current medical treatment of both children and adults with HPP.

Dental problems, rickets in children, and osteomalacia in adults are common in HPP. However, disease manifestations in individual patients are exceptionally variable. Recent studies broadened our understanding of HPP symptoms. For example, data showed behavioral health challenges in HPP children, and a large, real-world data set from the Global HPP Registry demonstrated that HPP adults regardless of the time of disease onset exhibit significant disease burden and are broadly affected by non-skeletal impairments, such as pain and chronic fatigue. Treatment for HPP relies on the enzyme replacement asfotase alfa. Small, mostly pediatric trials initially established dosing, safety and efficacy of asfotase alfa, and latest data corroborated the long-term safety and efficacy in both children and pediatric-onset adults. Data from several recent observational studies, including the Global HPP Registry, underscored that asfotase alfa improves physical functions, non-skeletal symptoms such as pain, and quality-of-life (QoL) in adults irrespective of age-of-onset. Clinical use of asfotase alfa is based on prescribing information and evidence-based consensus guidelines. However, recommendations for initiation of therapy are just emerging. Alternatives to asfotase alfa remain limited, but a derivative, efzimfotase alfa, currently undergoes clinical testing. Studies in larger HPP patient populations suggest efficacy of enzyme replacement therapy independent of patient age and time of disease onset.

Skeletal dysplasia (SD) is a large and heterogeneous group of rare genetic disorders that affects bone and cartilage growth. These disorders are diagnosed based on radiographic, clinical, and molecular criteria. However, the diagnostics is challenging due to clinical and genetic heterogeneity. We present the experience of systematic use of comprehensive genetic testing in the national health system and the molecular epidemiology of SD in Slovenia.

We retrospectively reviewed 470 patients with clinical features of SD, including prenatal, childhood, and adult patients referred for diagnostic genetic evaluation to the national genetic reference center over ten years. In 262 patients, whole exome or whole genome sequencing was performed, while direct gene sequencing was performed in 208 patients with a specific clinical diagnosis.

A definitive genetic diagnosis using NGS was achieved in 50% (n=131) of patients. Among the positive cases, 49.61% initially presented with a nonspecific diagnosis of SD, and genetic testing contributed to establishing the diagnosis. Moreover, we demonstrated high genetic heterogeneity in our SD cohort with 66 distinct causative genes, resulting in different types of SD. In detail, we detected 132 causative variants, of which 29 were novel, which expanded the mutational spectrum of SD. Furthermore, pathogenic copy number variants (CNVs) were identified in 4.55% of the total number of variants, highlighting the importance of CNV analysis in expanding the yield of molecular diagnosis of SD.

With the systematic use of WES and WGS, we have significantly improved the diagnostic yield of SD in the national health system and access to genetic testing. Moreover, we found significant genetic heterogeneity, and we report the genetic epidemiology of SD in the Slovenian population.

Hypophosphatasia (HPP) is a rare inherited metabolic disorder characterized by deficient activity of tissue-nonspecific alkaline phosphatase (TNAP) caused by variants in the ALPL gene. Disease manifestations encompass skeletal hypomineralization with rickets and lung hypoplasia, vitamin B6-dependent seizures, craniosynostosis, and premature loss of deciduous teeth. The clinical presentation can comprise failure to thrive with muscular hypotonia, delayed motor development, and gait disturbances later in childhood. In adults, pseudofractures are a characteristic indicator of severely compromised enzyme activity, but non-canonical symptoms like generalized musculoskeletal pain, weakness, and fatigue, frequently accompanied by neuropsychiatric and gastrointestinal issues are increasingly recognized as key findings in patients with HPP. The diagnosis is based on clinical manifestations in combination with persistently low alkaline phosphatase (ALP) activity, elevated levels of ALP substrates, specifically inorganic pyrophosphate (PPi), pyridoxal 5'-phosphate (PLP) or urine phosphoethanolamine (PEA), and genetic confirmation of a causative ALPL variant. Considering the wide range of manifestations, treatment must be multimodal and tailored to individual needs. The multidisciplinary team for comprehensive management of HPP patients should include expertise to ensure disease state metabolic and musculoskeletal treatment, dental care, neurological and neurosurgical surveillance, pain management, physical therapy, and psychological care. Asfotase alfa as first-in-class enzyme replacement therapy (ERT) for HPP has been shown to improve survival, rickets, and functional outcomes in severely affected children, but further research is needed to refine how enzyme replacement can also address emerging manifestations of the disease. Prospectively, further elucidating the pathophysiology behind the diverse clinical manifestations of HPP is instrumental for improving diagnostic concepts, establishing novel means for substituting enzyme activity, and developing integrative, multimodal care.

Hypophosphatasia (HPP) is an inherited metabolic disease caused by deficiency of tissue nonspecific alkaline phosphatase (TNAP) caused by pathogenic variants of the ALPL gene (MIM 171760). The clinical manifestations of HPP vary, ranging from a lethal perinatal-onset type to a moderate late-onset type presenting with nonspecific symptoms, such as arthropathy and musculoskeletal pain. HPP is characterized by low TNAP activity and defective bone mineralization, leading to bone deformity and skeletal abnormalities. Moreover, this disease can cause systemic complications, such as muscle weakness, seizures, pain, and respiratory failure, leading to premature death in infants. This study aimed to evaluate whether measuring TNAP activity in dried blood spots (DBSs) can identify patients with HPP. We developed an assay to assess TNAP activity using DBSs and screened 45 632 newborns born between February 2019 and March 2022 in Kumamoto Prefecture in Japan for HPP. We detected a single heterozygous variant of the ALPL gene in 5 newborns. During the clinical course follow-up, one newborn presented with HPP-related clinical manifestations. This is the first study on newborn screening (NBS) for HPP worldwide. NBS for HPP using DBSs may be practical and beneficial, as it is a high-throughput method. Moreover, the DBSs used for the TNAP assay are the same as those used for public-funded NBS worldwide. In the future, this system may be implemented as standard NBS for HPP.

Hypophosphatasia (HPP) is a common inherited skeletal disease. Early exfoliation of primary teeth is known as a dental manifestation of HPP, and sometimes this symptom leads to a diagnosis of HPP. This study aimed to investigate the dental manifestations of HPP in the Japanese population, focusing on dentition and occlusion. A total of 609 dental clinics among general hospitals with dentistry departments were invited to participate. Clinics were sent questionnaires about the number of HPP cases encountered from 2018 to 2022. When clinics indicated that they had treated HPP cases, we proceeded with a second questionnaire about the clinical dental findings of these cases. A total of 103 clinical records of HPP from 30 clinics were collected. Forty percent of non-odonto type cases showed enamel hypomineralization, which was significantly higher than the incidence found in odonto type cases (8.5%) (P < 0.001). Non-odonto type cases also exhibited malocclusion (40.0%), poor oral habits (29.1%), and dysphagia (23.6%). The number of dental visits made by HPP patients is increasing because of the development of new treatments and increased disease awareness. Dental symptoms of HPP vary in severity, with particularly severe forms of HPP associated with enamel hypomineralization, malocclusion, poor oral habits, and dysphagia. Patients with HPP require not only medical collaboration but also multidisciplinary dental care according to the severity of the disease.

We report a rare case of infantile hypophosphatasia associated with recurrent pneumonia, a condition with few similar cases documented globally. Clinical exome sequencing identified a heterozygous mutation in the alkaline phosphatase (ALPL) gene (c.69_74del; p.Glu23_Lys24del), the first such case reported in India and classified as 'likely pathogenic'. Its causality remains unproven due to limited evidence, including the absence of in vitro studies and pedigree analysis. Phenotypic variability may be influenced by factors such as incomplete penetrance, variable expressivity and environmental or epigenetic modifiers. This case highlights a rare but important cause of recurrent pneumonia in infants. Despite treatment, the child succumbed to severe pneumonia within 2 months. Clinicians should consider infantile hypophosphatasia in cases of recurrent pneumonia, motor delay, seizures, severe malnutrition and persistently low serum alkaline phosphatase. Further genetic and functional studies are needed to validate genotype-phenotype correlations and improve disease management.

Hypophosphatasia (HPP) is a congenital skeletal dysplasia. Enzyme replacement therapy (ERT) improves survival and bone mineralization of patients with perinatal severe HPP. However, there are few reports of ERT in patients with perinatal benign HPP, and its long-term efficacy remains unclear. Herein, we report the case of a boy with perinatal benign HPP who was initiated on early ERT with asfotase alpha. The patient was suspected of having HPP because of shortened limbs and deformed long bones on fetal 3D-CT. He was diagnosed with HPP based on clinical manifestations, low serum alkaline phosphatase levels, and ALPL gene variants. At the age of two years and three months, he had muscle weakness and motor developmental delay requiring support to walk, and ERT was initiated. His muscle strength improved immediately, and he could walk independently two months after starting ERT. Shortening and bowed limbs improved, and his body height increased from -3.48 SD (at the age of two years and three months) to -1.71 SD (at the age of nine years and eight months) after starting ERT. Hence, early ERT effectively improves motor development, bone deformity, and short stature in patients with perinatal benign HPP.

Hypophosphatasia (HPP) is an inherited error in metabolism resulting from loss-of-function variants in the ALPL gene, which encodes tissue-nonspecific alkaline phosphatase (TNAP). TNAP plays a crucial role in biomineralization of bones and teeth, in part by reducing levels of inorganic pyrophosphate (PPi), an inhibitor of biomineralization. HPP onset in childhood contributes to rickets, including growth plate defects and impaired growth. In adulthood, osteomalacia from HPP contributes to increased fracture risk. HPP also affects oral health. The dentoalveolar complex, that is, the tooth and supporting connective tissues of the surrounding periodontia, include 4 unique hard tissues: enamel, dentin, cementum, and alveolar bone, and all can be affected by HPP. Premature tooth loss of fully rooted teeth is pathognomonic for HPP. Patients with HPP often have complex oral health issues that require multidisciplinary dental care, potentially involving general or pediatric dentists, periodontists, prosthodontists, and orthodontists. The scientific literature to date has relatively few reports on dental care of individuals with HPP. Animal models to study HPP included global Alpl knockout mice, Alpl mutation knock-in mice, and mice with tissue-specific conditional Alpl ablation, allowing for new studies on pathological mechanisms and treatment effects in dental and skeletal tissues. Enzyme replacement therapy (ERT) in the form of injected, recombinant mineralized tissue-targeted TNAP has been available for nearly a decade and changed the prognosis for those with HPP. However, effects of ERT on dental tissues remain poorly defined and limitations of the current ERT have prompted exploration of gene therapy approaches to treat HPP. Preclinical gene therapy studies are promising and may contribute to improved oral health in HPP.

Mild hypophosphatasia (HPP) can be difficult to distinguish from other bone disorders in the absence of typical symptoms such as the premature loss of primary teeth. Therefore, this study aimed to analyze the crystallinity of hydroxyapatite (HAp) and the three-dimensional structure of collagen in HPP teeth at the molecular level and to search for new biomarkers of HPP. Raman spectroscopy was used to investigate the molecular structure, composition, and mechanical properties of primary teeth from healthy individuals and patients with HPP. The results showed that the crystallinity of HAp decreased and the carbonate apatite content increased in the region near the dentin-enamel junction (DEJ) of HPP primary teeth. X-ray diffraction (XRD) analyses confirmed a decrease in HAp crystallinity near the DEJ, and micro-computed tomography (CT) scanning revealed a decrease in mineral density in this region. These results suggest incomplete calcification in HPP primary dentin and may contribute to the development of diagnostic and therapeutic agents.

Adult hypophosphatasia is an uncommon inherited disorder of mineral homeostasis affecting bone. It arises from mutations within the Alkaline Phosphatase, Biomineralization Associated (ALPL) gene, which encodes tissue-nonspecific alkaline phosphatase. Because of its low prevalence and non-specific clinical manifestations, underdiagnosis and misdiagnosis are frequent, particularly in Asian populations.

We present a case of a 38-year-old Japanese male diagnosed with adult hypophosphatasia following consecutive tooth loss during orthodontic treatment. Genetic analysis revealed a compound heterozygous mutation within the ALPL gene. The patient remained asymptomatic until orthodontic treatment, suggesting that increased mechanical stress overwhelmed residual enzyme activity, triggering the hypophosphatasia symptoms. Asfotase Alfa enzyme replacement therapy improved healing following tooth extraction.

This case highlights the significance of including adult hypophosphatasia in the differential diagnosis for obscure dental complications arising during orthodontic procedures, particularly in Asian patients where certain ALPL variants may be more prevalent. Effective diagnosis and management of adult hypophosphatasia necessitate collaboration between orthodontic practitioners and medical specialists. Improved awareness and a multidisciplinary approach are crucial for timely diagnosis and successful intervention.

Hypophosphatasia (HPP) is a rare, inherited, and systemic disorder characterized by impaired skeletal mineralization and low tissue nonspecific serum alkaline phosphatase (TNSALP) activity. It is caused by either autosomal recessive or dominant-negative mutations in the gene that encodes TNSALP. The phenotype of HPP is very broad including abnormal bone mineralization, disturbances of calcium and phosphate metabolism, pain, recurrent fracture, short stature, respiratory impairment, developmental delay, tooth loss, seizures, and premature death. Other than supportive care, there has been no disease-specific treatment available for those with HPP. Asfotase alfa is a fully humanized, recombinant enzyme replacement therapy for the management of HPP. It is available in several countries for the treatment of the more severe forms of HPP, namely perinatal and infantile HPP. This review will summarize the preclinical data on asfotase alfa and highlight the data from clinical trials and case reports. These data show the transformative nature of asfotase alfa when administered as part of an interdisciplinary treatment model.

Hypophosphatasia (HPP; OMIM 241510, 241500, and 146300) is a progressive metabolic, genetic disease with wide clinical heterogeneity, ranging from perinatal lethality to mild or moderate localized symptoms. This study aims to analyze the perception of pain, quality of life, and access barriers to healthcare among patients diagnosed with hypophosphatasia in Colombia. In this document we present pain and quality of life results.

This study is an observational cohort of 18 HPP patients registered in the Colombian Association of Patients with Lysosomal Storage Diseases and Other Orphan Diseases (ACOPEL) database. We conducted a descriptive analysis using data from three questionnaires (SF-36, Brief Pain Questionnaire (BPQ), and Hypophosphatasia Impact Patient Survey (HIPS); the latter was translated into Spanish and validated for this study.

The most affected features, according to the SF-36 questionnaire, were overall health, vitality, and pain, with a median score above 67%. Patients' perception of their health status (HIPS questionnaire) was favorable, with 38.9% of cases reporting excellent health. On average, results from the BPQ indicated mild to moderate intensity of current pain experienced by patients. Consistency was observed in the reports of either the absence of pain or the presence of mild to moderate intensity when analyzing the results of the three questionnaires.

Colombian patients with HPP experience mild to moderate impairment in quality of life and pain that interfere with their daily activities. However, there is wide variability in the results obtained.

Hypophosphatasia (HPP) is a rare genetic disorder characterized by defective bone mineralization, leading to skeletal abnormalities and systemic complications. Asfotase alfa, a recombinant human tissue-nonspecific alkaline phosphatase (TNSALP) enzyme replacement therapy, has emerged as a promising treatment for HPP. However, a comprehensive evaluation of its efficacy and safety is warranted to guide clinical practice effectively.

The study followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered in Prospective Register of Systematic Reviews (PROSPERO). A search strategy across databases found studies on asfotase alfa for HPP. Two researchers independently extracted and assessed data. This systematic review examined how the drug impacted clinical outcomes such as survival rates, musculoskeletal symptoms, respiratory function, growth measurements, dental health, quality of life, and laboratory results.

This systematic review included 15 articles with a total of 455 HPP patients. Asfotase alfa was predominantly administered at a dose of 6 mg per kg per week among the reviewed studies. Notable findings included enhanced survival rates, relief from musculoskeletal pain, improvements in respiratory outcomes, growth parameters, dental health, and quality of life. Changes in laboratory variables indicated positive responses to treatment, including changes such as increase in alkaline phosphatase (ALP), decline in pyridoxal 5'-phosphate (PLP) and inorganic pyrophosphate (PPi) levels.

Asfotase alfa demonstrates efficacy in improving clinical outcomes and safety in patients with HPP. Its therapeutic benefits extend across various domains. However, Larger, age-stratified comparative studies are needed to further investigate the drug's effects in HPP patients.

Hypophosphatasia (HPP) is a rare inherited disorder characterized by the decreased activity of tissue-nonspecific alkaline phosphatase (TNSALP), caused by mutations in the ALPL gene. The aim of this study was to conduct differential diagnostics in HPP patients using whole-exome sequencing (WES). The medical records of HPP patients and the genetic testing of the ALPL gene were reviewed. Seven patients were recruited and underwent WES using the Illumina or MGI sequencing platforms. All of the exome samples were matched onto a GRCh38.p13 reference genome assembly by using the Genome Analysis ToolKit (GATK) and the BWA MEM read aligner. We present the clinical and molecular findings of the seven patients referred for genetic analyses due to a clinical and biochemical suspicion of HPP. In two patients out of three (with identified heterozygous variants in the ALPL gene), we also identified c.682T>A in exon 3 of the WNT10A gene and c.3470del in exon 23 of the SMC1A gene variants for the first time. In four patients, variants in the ALPL gene were not detected, but WES allowed us to identify for the first time rare variants (c.5651A>C in exon 36 of the TRIO gene, c.880T>G in exon 6 of the TRPV4 gene, c.32078-1G>T in intron 159 of the TTN gene, c.47720_47721del in exon 235 of the TTN gene, and c.1946G>A in exon 15 of the SLC5A1 gene) and to conduct differential diagnostics with HPP. Using WES, for the first time, we demonstrate the possibility of early differential diagnostics in HPP patients with other rare genetic diseases.

Hypophosphatasia (HPP) is a rare, inherited metabolic disease caused by deficient activity of tissue-nonspecific alkaline phosphatase (TNSALP). Efzimfotase alfa (ALXN1850) is a second-generation TNSALP enzyme replacement therapy in development for HPP. This first-in-human open-label, dose-escalating phase 1 trial evaluated efzimfotase alfa safety, tolerability, pharmacokinetics, pharmacodynamics, and immunogenicity. Fifteen adults (5/cohort) with HPP received efzimfotase alfa in doses of 15 mg (cohort 1), 45 mg (cohort 2), or 90 mg (cohort 3) as one intravenous (i.v.) dose followed by 3 weekly subcutaneous (s.c.) doses. The primary objective was to assess safety and tolerability. Secondary objectives included pharmacokinetics, pharmacodynamics of ALP substrates known to be biomarkers of disease (inorganic pyrophosphate [PPi] and pyridoxal 5'-phosphate [PLP]) and immunogenicity. Treatment-emergent adverse events (TEAEs) occurred in 12 (80%) participants. Eight (53%) participants had injection site reactions (ISRs), observed after 10 of 41 (24%) s.c. injections. Most ISR TEAEs were mild and resolved within 1-2 d. Peak and total exposures of efzimfotase alfa increased in a greater-than-dose proportional manner over the range of 15-90 mg after i.v. and s.c. dosing. The arithmetic mean elimination half-life was approximately 6 d; absolute bioavailability was 28.6%-36.8% over the s.c. dose range of 15-90 mg. Dose-dependent reductions in plasma concentrations of PPi and PLP relative to baseline reached nadir in the first week after i.v. dosing and were sustained for 3-4 wk after the last s.c. dose. Four (27%) participants tested positive for antidrug antibodies (ADAs), 3 of whom were ADA positive before the first dose of efzimfotase alfa. ADAs had no apparent effect on efzimfotase alfa pharmacokinetics/pharmacodynamics. No participants had neutralizing antibodies. Efzimfotase alfa demonstrated acceptable safety, tolerability, and pharmacokinetic profiles and was associated with sustained reductions in biomarkers of disease in adults with HPP, supporting further evaluation in adult and pediatric patients. Registration: ClinicalTrials.gov NCT04980248 (https://clinicaltrials.gov/study/NCT04980248).

Metabolic bone diseases are a heterogenous group of conditions that all result in aberrant bone mineral homeostasis with resulting skeletal disease. The underlying causes are variable, ranging from nutritional deficiencies to pathogenic variants in skeletal genes. To properly diagnose and treat these conditions, a clinician needs to understand bone metabolism as well as recognize the signs of disease in a patient. This review will focus on three relatively common metabolic bone diseases (osteogenesis imperfecta, hypophosphatasia, and X-linked hypophosphatemic rickets) that are caused by genetic variants, not by nutritional deficiency. As molecular DNA sequencing has improved, the scientific community has been able to better understand the genetic basis of these conditions and create sophisticated medical treatments based on the genetic deficiency.

Hypophosphatasia (HPP) is a rare disorder, resulting from loss-of-function variants of the ALPL gene encoding non-tissue specific alkaline phosphatase (TNSALP). Presentation varies largely, with increased severity usually occurring with earlier disease onset. Here we describe the clinical improvement of a 57-year-old woman with childhood onset HPP, after initiating treatment with asfotase alfa (Strensiq®). This was started because of the rapid and progressive radiological deterioration of bone structure after placement of nails in both upper legs for spontaneous atypical femur fracture (AFF) - like fractures. Initiation of treatment, not only resulted in stabilization of bone structure on X-rays, but within a few weeks there was a dramatic reduction of burning pain sensations in the lower legs, attributed in retrospect to neuropathic pain, and also almost complete disappearance of headaches. Additionally, unhealed metatarsal fractures finally healed after almost 10 years. Drug efficacy was further evaluated through -quality of life questionnaires and multiple tests conducted by the physiotherapist, and showed clear improvements. Within 3 months after starting asfotase alfa, the patient was able to carry out her daily tasks indoors without relying on a walker and even started electric bike rides for 20 km/day. In conclusion, treatment with asfotase alfa, halted rapid radiological bone deterioration after bilateral intramedullary femoral pen placement and strongly increased quality of life, marked by rapid disappearance of neuropathic pain, reduction in headaches and musculoskeletal pains, and enhanced muscle strength and mobility. The quick and almost complete disappearance of neuropathic pain and headache suggests a relation with disturbed levels of metabolites in HPP.

The diagnosis and management of metabolic bone disease among children can be challenging. This difficulty could be due to many factors, including limited awareness of these rare conditions, the complex pathophysiology of calcium and phosphate homeostasis, the overlapping phenotype with more common disorders (such as rickets), and the lack of specific treatments for these rare disorders. As a result, affected individuals could experience delayed diagnosis or misdiagnosis, leading to improper management. In this review, we describe the challenges facing diagnostic and therapeutic approaches to two metabolic bone disorders (MBD) among children: hypophosphatasia (HPP) and X-linked hypophosphatemia (XLH). We focus on explaining the pathophysiological processes that conceptually underpin novel therapeutic approaches, as well as these conditions' clinical or radiological similarity to nutritional rickets. Particularly in areas with limited sun exposure and among patients not supplementing vitamin D, nutritional rickets are still more common than HPP and XLH, and pediatricians and primary physicians frequently encounter this disorder in their practices. More recently, our understanding of these disorders has significantly improved, leading to the development of novel therapies. Asfotas alfa, a recombinant, human- tissue, nonspecific alkaline phosphatase, improved the survival of patients with HPP. Burosumab, a human monoclonal anti-FGF23 antibody, was recently approved as a specific therapy for XLH. We also highlight the current evidence on these two specific therapies' safety and effectiveness, though long-term data are still needed. Both HPP and XLH are multisystemic disorders that should be managed by multidisciplinary teams. Finally, recognizing these conditions in early stages will enable affected children and young adults to benefit from newly introduced, specific therapies.

Hypophosphatasia (HPP) is an inherited disease caused by variants of the ALPL gene encoding tissue-nonspecific alkaline phosphatase. Adult-onset HPP (adult HPP), known as a mild form of HPP, develops symptoms involving osteomalacia after the age of 18 years. Asfotase alfa (AA) is a modulated recombinant human alkaline phosphatase (ALP) that has been established as a first-line therapy for severe forms of HPP, such as perinatal and infantile forms. We described a 64-year-old female who presented with pseudofractures in bilateral femur diaphyses and impaired mobility. Low serum ALP activity and a high concentration of urine phosphoethanolamine indicated the diagnosis of HPP, which was confirmed by the identification of a homozygous variant in the ALPL gene (c.319G > A; p.Val107Ile). An in vitro transfection experiment to measure the ALP activity of this novel variant protein was performed, resulting in 40% of the residual enzymatic activity compared with the wild type. AA was initiated to facilitate the union of pseudofracture and to improve mobility. After 6 months, radiographic images revealed the disappearance of fracture lines, and improvement of ambulatory ability was confirmed by the 6-minute walk test (525 to 606 m). The EQ-5D-5L index was also improved (0.757 to 0.895). Within a follow-up period, the levels of urine pyrophosphate corrected by urine creatinine (uPPi/Cre) declined in parallel with the level of plasma PPi (plasma PPi: 6.34 to 1.04 μM, uPPi/Cre: 226.8 to 75.4 nmol/mg). The beneficial effect of AA on pseudofracture healing in adult HPP was presented, although the application of AA should be restricted to patients exhibiting relatively severe manifestations. In addition, a novel pathogenic variant of the ALPL gene was identified with the supportive result of functional analysis. Furthermore, when monitoring patients with HPP treated with AA, uPPi/Cre might be a convenient substitute for plasma PPi, which requires immediate filtration after blood sampling. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Hypophosphatasia (HPP) is a rare condition characterized by abnormal bone mineralization. The manifestations of HPP vary from no symptoms to intrauterine fetal death; short stature is another indication of HPP. A 3 ½-year-old boy presented with short stature, transient hypercalcemia, and mild gait disturbance without definite bony deformity. Laboratory examination revealed transient hypercalcemia, normal phosphorous and 25-hydroxy vitamin D levels, and mildly low alkaline phosphatase levels. A targeted next-generation sequencing panel associated with inborn errors of metabolism revealed a pathogenic heterozygous mutation in the ALPL gene, c.979T>C (p.Phe327Leu). When a child visits a hospital with short stature, decreased height velocity, and low alkaline phosphatase level, clinicians should consider the possibility of HPP even if definite skeletal dysplasia is not evident.

Enzymes are used to treat a wide variety of human diseases, including lysosomal storage disorders, clotting disorders, and cancers. While enzyme therapeutics catalyze highly specific reactions, they often suffer from a lack of cellular or tissue selectivity. Targeting an enzyme to specific disease-driving cells and tissues can mitigate off-target toxicities and provide novel therapeutic avenues to treat otherwise intractable diseases. Targeted enzymes have been used to treat cancer, in which the enzyme is either carefully selected or engineered to reduce on-target off-tumor toxicity, or to treat lysosomal storage disorders in cell types that are not addressed by standard enzyme replacement therapies. In this review, we discuss the different targeted enzyme modalities and comment on the future of these approaches.

Hypophosphatasia (HPP) is a rare, heritable metabolic disorder caused by deficient activity of tissue-nonspecific alkaline phosphatase (TNSALP). Asfotase alfa (AA) is a human recombinant TNSALP that promotes bone mineralization and is approved to treat eligible patients with HPP.

This prospective single-center observational study evaluated AA in adults with pediatric-onset HPP over 2 years of treatment (ClinicalTrials.govNCT03418389). Primary outcomes evaluated physical function; secondary outcomes assessed quality of life (QoL) and pain.

The study included 17 females and 5 males (mean age: 48.7 years). Median distance walked in the 6-Minute Walk Test increased significantly from baseline to 12 months (P = 0.034) and results were sustained. Median Timed Up and Go test time significantly decreased from baseline at 12 (P = 0.003) and 24 months (P = 0.005), as did the median chair rise time test at 12 (P = 0.003) and 24 months (P < 0.002). The change from baseline in usual gait speed was significant at 12 (P = 0.003) and 24 months (P = 0.015). Mean dominant and nondominant hand grip strength improved at 24 months (P = 0.029 and P = 0.019, respectively). Median Short Form 36 Physical Component Summary scores significantly improved from baseline at 12 (P = 0.012) and 24 (P = 0.005) months, and median Lower Extremity Functional Scale scores improved from baseline at 12 (P = 0.001) and 24 (P = 0.002) months. No significant change was noted in pain level at these timepoints. While injection site reactions occurred in 86.4 % of the participants, there were no severe side effects or safety findings.

Adults with pediatric-onset HPP treated with AA experienced marked improvement in functional and QoL outcomes that were observed as early as within 3 months of initial treatment and were sustained over 24 months.

Hypophosphatasia (HPP) is characterized by severe skeletal symptoms including mineralization defects, insufficiency fractures, and delayed facture healing or non-unions. HPP is caused by mutations of the tissue non-specific alkaline phosphatase (TNSALP). Zinc is a cofactor of TNSALP and vitamin D an important regulator of bone matrix mineralization. Data from this retrospective study indicates that deficiencies in zinc or vitamin D occur in HPP patients with a similar frequency as in the general population. While guidelines for repletion of these micronutrients have been established for the general population, the transferability of the efficacy and safety of these regiments to HPP patients still needed to be determined. We filtered for variant classification (ACMG 3-5, non-benign) and data completeness from a total cohort of 263 HPP patients. 73.5 % of this sub-cohort were vitamin D deficient while 27.2 % were zinc deficient. We retrospectively evaluated the effect of supplementation according to general guidelines in 10 patients with zinc-deficiency and 38 patients with vitamin d-deficiency. The treatments significantly raised serum zinc or vitamin D levels respectively. All other assessed disease markers (alkaline phosphatase, pyrodoxal-5-phosphate) or bone turnover markers (phosphate, calcium, parathyroid hormone, bone specific alkaline phosphatase, creatinine, desoxypyridinoline) remained unchanged. These results highlight that general guidelines for zinc and vitamin D repletion can be successfully applied to HPP patients in order to prevent deficiency symptoms without exacerbating the disease burden or causing adverse effects due to changes in bone and calcium homeostasis.

Hypophosphatasia (HPP) is a rare inherited disorder, caused by mutations in the alkaline phosphatase (ALPL) gene, which encodes for the tissue non-specific alkaline phosphatase (TNSALP) isoform of alkaline phosphatase (ALP). Adult HPP is one of the mild forms that presents with unspecific signs such as osteopenia, osteomalacia and muscle involvement. Our purpose was to identify and characterize possibly misdiagnosed adult HPP patients at a clinical and biochemical level.

At the laboratory of Miguel Servet University Hospital we retrospectively reviewed serum ALP levels in adults over a 48-month period. The clinical records of individuals with consistently low ALP levels were reviewed to exclude secondary causes. Those with persistent hypophosphatasemia were screened for symptoms of HPP. The study participants were evaluated at biochemical and genetic levels.

We identified 705 ALP determinations (out of 384,000 processed) in 589 patients below the reference range (30 U/l). Only 21 patients with clinical signs and symptoms of HPP were selected for genetic testing. Finally, only 12 patients participated in the study, 83.3% of whom (10/12) harbored a pathogenic or likely pathogenic variant in a heterozygous state. The major symptoms of our cohort were the presence of musculoskeletal pain (100% of patients) and muscular weakness (83.3% patients).

Mild HPP patients presenting with diffuse symptoms such as musculoskeletal pain may be undiagnosed or misdiagnosed as osteoporosis patients by routine diagnosis. It is important to identify these individuals, to avoid inappropriate treatment with antiresorptive drugs.

The objective of this study was to better understand the clinical profiles of children with hypophosphatasia (HPP) prior to treatment with enzyme replacement therapy (ERT).

Pretreatment demographics and medical histories of ERT-treated children (aged <18 years) enrolled in the Global HPP Registry (2015-2020) were analyzed overall, by age at first HPP manifestation (<6 months vs. 6 months to 18 years), and by geographic region (USA/Canada, Europe, and Japan).

Data from 151 children with HPP were analyzed. Sex distribution was balanced overall (52.3% female; 47.7% male) but differed in Japan (63.0% female; 37.0% male). Prior to ERT initiation, common manifestations were skeletal (67.5%) and extraskeletal, with the foremost types being muscular (48.3%), constitutional/metabolic (47.0%), and neurologic (39.7%). A high proportion of children who first presented at <6 months of age (perinatal/infantile period) had a history of bone deformity (59.3%) and respiratory failure (38.3%), while those aged 6 months to 18 years at first manifestation had a predominance of early loss of primary teeth (62.3%) and gross motor delay (41.0%). Those from Japan were reported to have a younger median age overall, the highest proportion of skeletal manifestations (80.4%) and growth impairment, while European data reported the highest proportion of muscular manifestations (70.7%). In the USA/Canada, skeletal and muscular manifestations were reported at the same frequency (57.4%).

Prior to ERT, skeletal and extraskeletal manifestations were commonly reported in children with HPP, with differences by age at first HPP manifestation and geographical region. Comprehensive assessments of children with HPP are warranted prior to ERT initiation.

Hypophosphatasia (HPP) is a life-threatening disease that occurs due to the mutation of the TNSALP (Tissue nonspecific isoenzyme of alkaline phosphatase) encoding gene. There is no approved treatment for Hypophosphatasia. Therefore, the only effective treatment for HPP is enzyme replacement therapy using the drug asfotase alfa which increases the patient's life span. The aim of the study is to evaluate the effectiveness and safety of asfotase alfa (enzyme replacement therapy) in treating HPP. A Literature search was done using PubMed, Google scholar, science direct, and Wiley LILACS utilizing MeSH keywords such as - Hypophosphatasia and asfotase alfa. A total of 411 articles were screened, of which four articles were taken for this qualitative analysis. Reporting of this systematic review is done by using PRISMA guidelines. Asfotase alfa/enzyme replacement therapy is examined on patients with different age groups and on congenital HPP patients to assess the effectiveness of HPP treatment. Enzyme replacement therapy using asfotase alfa is an effective and assured treatment for infants, children, and adults suffering from HPP.

Hypophosphatasia (HPP) is an inherited disease caused by a low activity of tissue-nonspecific alkaline phosphatase, a hydrolase that removes phosphate groups from many molecules. Decreased alkaline phosphatase activity leads to the accumulation of three main metabolites, i.e., pyridoxal 5´-phosphate (PLP), inorganic pyrophosphate (PPi), and phosphoethanolamine. Impairment in PLP dephosphorylation induces seizures, while PPi accumulation inhibits bone mineralization. Clinically, HPP has a wide spectrum of presentations, ranging from neonatal death to an apparent lack of symptoms. This disease is classified into six subtypes according to the age at onset of first signs or symptoms. The clinical manifestations of the disease include rickets-like bone changes, bone demineralization, fragility fractures, reduced muscular strength, chest deformity, pulmonary hypoplasia, nephrolithiasis, nephrocalcinosis, and chondrocalcinosis. Treatment of HPP consists of enzyme replacement therapy. Before this therapy was approved, treatment was palliative and associated with high morbidity and mortality. Asfotase alfa has changed the prognosis of the disease by reducing bone deformity and improving bone mineralization, lung function, and muscle weakness, among other benefits. In adults, teriparatide and anti-sclerostin antibody have been used off-label in selected cases, demonstrating benefit in accelerating fracture healing and in concomitant treatment of osteoporosis. This review summarizes the main aspects of HPP and identifies the particularities of the disease in adult patients.

Hypophosphatasia (HPP) is a congenital disorder caused by mutations in the tissue-nonspecific alkaline phosphatase (TNALP) gene. The pathogenesis of HPP varies, ranging from severe cases in which there is total absence of fetal bone calcification, which leads to stillbirth, to relatively mild cases in which the effects are confined to the teeth, such as early loss of the primary teeth. In recent years, the establishment of enzyme supplementation as a treatment method has prolonged survival in patients; however, this approach does not provide sufficient improvement for failed calcification. Furthermore, the effects of enzyme replacement therapy on the jawbone and periodontal tissues have not yet been studied in detail. Therefore, in this study, we investigated the therapeutic effects of enzyme replacement therapy on jawbone hypocalcification in mice. Recombinant TNALP was administered to mothers before birth and newborns immediately after birth, and the effect of treatment was evaluated at 20 days of age. The treated HPP mice had improved mandible (mandibular length and bone quality) and tooth quality (root length of mandibular first molar, formation of cementum), as well as improved periodontal tissue structure (structure of periodontal ligament). Furthermore, prenatal treatment had an additional therapeutic effect on the degree of mandible and enamel calcification. These results suggest that enzyme replacement therapy is effective for the treatment of HPP, specifically in the maxillofacial region (including the teeth and mandible), and that early initiation of treatment may have additional beneficial therapeutic effects.

Hypophosphatasia (HPP) is an inherited, systemic disorder, caused by loss-of-function variants of the ALPL gene encoding the enzyme tissue non-specific alkaline phosphatase (TNSALP). HPP is characterized by low serum TNSALP concentrations associated with defective bone mineralization and increased fracture risk. Dental manifestations have been reported as the exclusive feature (odontohypophosphatasia) and in combination with skeletal complications. Enzyme replacement therapy (asfotase alfa) has been shown to improve respiratory insufficiency and skeletal complications in HPP patients, while its effects on dental status have been understudied to date. In this study, quantitative backscattered electron imaging (qBEI) and histological analysis were performed on teeth from two patients with infantile HPP before and during asfotase alfa treatment and compared to matched healthy control teeth. qBEI and histological methods revealed varying mineralization patterns in cementum and dentin with lower mineralization in HPP. Furthermore, a significantly higher repair cementum thickness was observed in HPP compared to control teeth. Comparison before and during treatment showed minor improvements in mineralization and histological parameters in the patient when normalized to matched control teeth. HPP induces heterogeneous effects on mineralization and morphology of the dental status. Short treatment with asfotase alfa slightly affects mineralization in cementum and dentin. Despite HPP being a rare disease, its mild form occurs at higher prevalence. This study is of high clinical relevance as it expands our knowledge of HPP and dental involvement. Furthermore, it contributes to the understanding of dental tissue treatment, which has hardly been studied so far.

Hypophosphatasia (HPP) is a genetic disease caused by loss-of-function mutations in ALPL, which encodes tissue-nonspecific alkaline phosphatase (ALP). Early diagnosis and treatment of perinatal and infantile HPP are important because of their high mortality rates. Enzyme replacement therapy (ERT) using human recombinant tissue-nonspecific ALP asfotase alfa was introduced in Korea in 2016. We report the first experience of ERT over 6 years for perinatal lethal and infantile HPP in Korea.

The first patient was a 6-week-old Korean boy with a failure to thrive. The second patient was an 8-day-old Korean-Uzbek body with generalized tonic-clonic seizure with cyanosis.

HPP was suspected in both patients because of the very low level of ALP activity and rachitic findings on radiographs, and the disease was confirmed by Sanger sequencing of the ALPL gene.

The first patient with infantile HPP started ERT at 21 months of age and the second patient with perinatal HPP started ERT at 30 days of age. Both patients received asfotase alfa (2 mg/kg 3 times per week subcutaneously, adjusted to 3 mg/kg 3 times per week if required) for 6 years.

After 6 years of ERT, radiographic findings and growth standard deviation scores improved in both patients. The second patient showed no evidence of rickets after 3 years of ERT. Mechanical respiratory support and supplemental oxygen were not required after 4.5 years of treatment in the first patient and at 2 months after treatment in the second patient.

Among the 2 patients, the patient who started ERT early had a much better prognosis despite a more severe initial clinical presentation. Our results suggest that early diagnosis and prompt treatment play an important role in improving long-term prognosis and avoiding morbidity and premature mortality in patients with perinatal and infantile HPP.