Maturity-onset diabetes of the young type 9 or latent autoimmune diabetes in adults: A case report and review of literature

Abstract

BACKGROUND

Maturity-onset diabetes of the young (MODY) is a monogenic genetic disease often clinically misdiagnosed as type 1 or type 2 diabetes. MODY type 9 (MODY9) is a rare subtype caused by mutations in the PAX4 gene. Currently, there are limited reports on PAX4-MODY, and its clinical characteristics and treatments are still unclear. In this report, we described a Chinese patient with high autoimmune antibodies, hyperglycemia and a site mutation in the PAX4 gene.

CASE SUMMARY

A 42-year-old obese woman suffered diabetes ketoacidosis after consuming substantial amounts of beverages. She had never had diabetes before, and no one in her family had it. However, her autoantibody tested positive, and she managed her blood glucose within the normal range for 6 mo through lifestyle inter-ventions. Later, her blood glucose gradually increased. Next-generation sequencing and Sanger sequencing were performed on her family. The results revealed that she and her mother had a heterozygous mutation in the PAX4 gene (c.314G>A, p.R105H), but her daughter did not. The patient is currently taking liraglutide (1.8 mg/d), and her blood glucose levels are under control. Previous cases were retrieved from PubMed to investigate the relationship between PAX4 gene mutations and diabetes.

CONCLUSION

We reported the first case of a PAX4 gene heterozygous mutation site (c.314G>A, p.R105H), which does not appear pathogenic to MODY9 but may facilitate the progression of latent autoimmune diabetes in adults.

Key Words: Maturity-onset diabetes of the young, PAX4, Latent autoimmune diabetes in adults, Type 1 diabetes, Case report

Core Tip: Maturity-onset diabetes of the young type 9 (MODY9), as a subtype of MODY caused by mutations in the PAX4 gene, has been poorly reported, and its clinical features and treatments remain unclear. We reported a heterozygous mutation in the PAX4 gene (c.314G>A, p.R105H) in a patient with latent autoimmune diabetes in adults (LADA). Based on the analysis of the cases indexed in PubMed, it is the first reported case of PAX4 with LADA. The PAX4 heterozygous mutation reported in the present case may not be considered for MODY9 and may be facilitated for the onset and progress of LADA.

INTRODUCTION

Maturity-onset diabetes of the young (MODY) is a monogenic genetic disease inherited predominantly and is often associated with impaired pancreatic β cell function[1,2]. The prevalence in adults is estimated to be 1 in 10000 and in children to be 1 in 23000, accounting for 1%-3% of diabetes cases[3,4]. A definitive diagnosis of MODY relies on genetic testing. According to the Standard of Care for Diabetes proposed in 2022[5], children diagnosed with diabetes within 6 mo or children or young adults who do not have typical characteristics of type 1 or type 2 diabetes but have a family history of diabetes for several generations should have genetic testing for MODY. MODY is often misdiagnosed as type 1 or type 2 diabetes[6,7].

MODY is classified into subtypes based on genetic mutations; 14 gene mutations have been proven to cause MODY. The most common types are HNF4A, GCK and HNF1A[8]. MODY9 is a subtype caused by mutations in the PAX4 gene. PAX4 belongs to the paired cassette homology domain family primarily expressed in pancreatic islets and is a key factor in the normal differentiation of β cells and δ cells[9]. Inactivation of PAX4 causes a lack of mature β and δ cells in the pancreas, resulting in the body’s inability to produce sufficient insulin and growth inhibitory hormone[10]. Numerous studies have shown that PAX4 can promote the differentiation of stem cells to β cells[11,12], promote β cell survival and proliferation[13,14], induce the conversion of mature α cells to β cells[15,16], regulate cell cycle proteins[17] and maintain endoplasmic reticulum integrity[18] and other pathways that play a crucial role in diabetes. Reports on the diagnosis of PAX4 mutations are still controversial, and the clinical features and treatment of PAX4-related hyperglycemia have not been identified. Here, we reported a patient with high autoimmune antibodies and hyperglycemia with a novel site mutation in the PAX4 gene.

CASE PRESENTATION

Chief complaints

A 42-year-old woman presented with xerostomia, polydipsia, polyuria and blurred vision for 4 d.

History of present illness

The patient experienced xerostomia, polydipsia and polyuria after consuming substantial amounts of beverages and fruits 4 d before admission to the local hospital. She also had blurred vision and fatigue. She went to the local hospital, where her lab results revealed that her fasting blood glucose (FBG) was 18.15 mmol/L, and her glycated hemoglobin (HbA1c) was 10.3%. She was then prescribed metformin and another oral drug (details unknown) to control her blood glucose. However, her symptoms were not relieved, and her FBG remained at 14.54 mmol/L at the time of admission.

History of past illness

The patient had a history of cesarean section 18 years prior to admission and had uterine fibroids for 12 years.

Personal and family history

The patient reported no knowledge of diabetes in her family.

Physical examination

The patient was sane, conscious and had dry lips. Her body mass index was 31.85 kg/m², and her blood pressure was 133/96 mmHg. She was generally in good condition, and no other obvious abnormality was detected at admission.

Laboratory examinations

At admission, the patient arterial pH was 7.29, PO₂ was 93 mmHg, bicarbonate was 14.6 mmol/L, FBG was 14.54 mmol/L, islet cell antibody was 45 times higher than normal, glutamic acid decarboxylase (GAD) was 200 times higher than normal, and insulin autoantibody was two times higher than normal. Her urine ketone was significantly positive. Her liver function was slightly abnormal, but her blood lipids, albumin/creatinine ratio and thyroid function were normal (Table 1).

Table 1 Clinical features and laboratory results of the patient.

Parameter	Values
Age at onset (yr)	42
Weight (kg)	79.5
Height (cm)	158
BMI (kg/m2)	31.85
FBG (mmol/L)	14.54
HbA1c (%)	10.3
pH	7.29
HCO3- (mmol/L)	14.6
ABE	16.6
SBE	16.7
ICA (COI)	45.20
GAD (IU/mL)	> 2000.00
IAA (COI)	2.10
KET (mmol/L)	+-
UA (µmol/L)	484.7
TG (mmol/L)	1.23
TC (mmol/L)	4.22
HDL (mmol/L)	1.01
LDL (mmol/L)	2.89
ALT (U/L)	44.8
AST (U/L)	40.4
ALP (U/L)	66.6
GGT (U/L)	34.0

ABE: Actual base excess; ALP: Alkaline phosphatase; ALT: Alanine transaminase; AST: Aspartate transaminase; BMI: Body mass index; FBG: Fasting blood glucose; GAD: Glutamic acid decarboxylase; GGT: γ-glutamyl transpeptidase; HbA1c: Glycated hemoglobin; HCO₃^-: Bicarbonate; HDL: High-density lipoprotein cholesterol; IAA: Insulin autoantibodies; ICA: Islet cell autoantibodies; KET: Urinary ketones; LDL: Low-density lipoprotein cholesterol; SBE: Standard base excess; TC: Total cholesterol; TG: Triglyceride; UA: Uric acid.

Next-generation sequencing

The patient was tested with next-generation sequencing (DNBSEQ-T7) to detect 130 genes related to diabetes, which include 14 pathogenic genes associated with MODY (HNF4A, GCK, HNF1A, PDX1, HNF1B, NEUROD1, KLF11, CEL, PAX4, INS, BLK, ABCC8, KCNJ11, APPL1). The patient’s mother and daughter also underwent Sanger validation. The findings revealed that she had a heterozygous mutation in the PAX4 gene (c.314G>A, p.R105H), and subsequent Sanger validation revealed that her mother also suffered the same mutation. Her daughter was normal (Figure 1).

Figure 1 Sequencing profile of exon 5 of PAX4 in the mutation region (R105H). A: Sequencing result of the propositus; B: Sequencing result of the mother; C: Sequencing result of the daughter. The whole exome sequencing and Sanger sequencing verification showed the propositus and her mother had the heterozygous variant of PAX4, c.314G>A; p.R105H, and the daughter was normal.

FINAL DIAGNOSIS

Diabetic ketoacidosis and type 1 diabetes mellitus (T1DM).

TREATMENT

The patient was given a fluid replacement and insulin treatment at admission until her arterial pH and urine ketone levels returned to normal. She was then administered a hypodermic injection of mixed protamine zinc recombinant human insulin injection (70/30), 8 IU before breakfast and 8 IU before dinner, and her FBG level was 6-7 mmol/L at discharge. She maintained lifestyle interventions (balanced diet and regular exercise 30 min/d). One month after discharge, the patient discontinued insulin therapy, and her blood glucose appeared to be normal with lifestyle interventions.

OUTCOME AND FOLLOW-UP

The patient visited our outpatient clinic regularly for check-ups. She also regularly tested capsular blood glucose at home, and the data showed her blood glucose was well controlled. About 3 mo after discharge, we administered an oral glucose tolerance test (OGTT) to evaluate her cell function. Her HbA1c was 6.2%, OGTT (fasting, 30 min, 1 h and 2 h) was 5.96 mmol/L, 12.44 mmol/L, 12.64 mmol/L and 8.33 mmol/L, respectively, oral glucose-insulin release test (fasting, 30 min, 1 h and 2 h) was 6.82 µU/mL, 35.97 µU/mL, 44.81 µU/mL and 56.74 µU/mL, respectively, and the autoantibodies of GAD were still higher than the upper limit. At the 9-mo follow-up, she informed us that her capsular blood glucose was always around 7 mmol/L or slightly higher; hence, we further scheduled an HbA1c and an OGTT test. Her HbA1c was 7.3%, OGTT (fasting, 30 min, 1 h and 2 h) was 8.88 mmol/L, 11.26 mmol/L, 15.72 mmol/L and 18.17 mmol/L, respectively, and oral glucose-insulin release test (fasting, 30 min, 1 h and 2 h) was 11.93 µU/mL, 18.26 µU/mL, 30.93 µU/mL and 33.13 µU/mL. Furthermore, her GAD was still higher than the upper limit (GAD ≥ 10.0 IU/mL). Considering her gradually increasing blood glucose and relatively remaining cell function, she was administered liraglutide 1.8 mg once a day. Her fasting blood glucose was 5-6 mmol/L, and her postprandial blood glucose was 6-8 mmol/L (Figure 2).

Figure 2 Changes of blood glucose and serum insulin during the follow-up. A: Fasting blood glucose levels from onset to follow-up; B: Oral glucose tolerance test levels during follow-up; C: Oral glucose-insulin release test levels during follow-up. FBG: Fasting blood glucose; OGTT: Oral glucose tolerance test; OGIRT: Oral glucose-insulin release test.

DISCUSSION

Here, we reported a rare case of diabetes with a heterozygous mutation in the PAX4 gene (c.314G>A, p.R105H). The patient, a middle-aged obese woman, had no obvious diabetic syndrome until she consumed substantial amounts of beverages and fruits. Her HbA1c was 10.3%, indicating that her blood glucose was increased for at least 3 mo. Her high body mass index and insidious onset diabetes are characteristics of type 2 diabetes. However, the repeated high level of autoantibodies (GAD, islet cell antibody and insulin autoantibody) suggested the diagnosis of latent autoimmune diabetes in adults (LADA). Furthermore, this was further supported by her short remission time after lifestyle interventions (about 3-6 mo) and progressive declining cell function and increased blood glucose. We performed genetic testing to exclude other reasons for hyperglycemia. We found that the patient and her mother had a heterozygous mutation in the PAX4 gene (c.314G>A, p.R105H), while her daughter did not. We then drew her family pedigree (Figure 3), which confirmed that the mutation was indeed heterozygous, and the mother carried the mutation but with normal blood glucose. Therefore, we concluded that the mutation might not be the primary cause of her hyperglycemia. So, we did not diagnose her with MODY. To the best of our knowledge, this is the first case of LADA combined with a heterozygous mutation in the PAX4 gene.

Figure 3 Family pedigree of the patient. To the right of the symbol, it shows the genotype of PAX4 c.314G>A mutation. M: Mutant allele; N: Normal allele.

MODY9 is the result of a PAX4 mutation. However, few studies have reported MODY9 in detail. Here, we conducted a literature review of case reports of PAX4 mutation. We searched the PubMed database with the terms “maturity-onset diabetes of the young or MODY” and “paired cassette homology domain or PAX4” and selected the case reports, pedigree analyses, and cross-sectional studies. If the article was not related to MODY9 or PAX4 gene mutations, or if the specifics of the patient were not described, it was excluded. Finally, nine articles with 17 cases were included[19-27] (Table 2).

Table 2 Articles describing the characteristics of clinical cases carrying the PAX4 mutant gene.

Ref.	Diagnosis	PAX4 variant	Ethnicity	Family history	Diagnostic age (yr)	Sex	BMI (kg/m2)	HbA1c, %	Insulin antibody, +/-	Treatment	HbA1c % at remission
Sujjitjoon et al[22]	MODY9	Heterozygous IVS7-1G>A	Thailand	Yes	44	Female	NA	NA	-	NA	NA
Chapla et al[25]	MODY	Heterozygous c.92G>T	Asian-Indian	Yes	14	Male	23	NA	-	Glimepiride and insulin	NA
Jo et al[19]	MODY	Heterozygous c.374-412 del 39	Japanese	Yes	15	Male	18.2	14.5	-	Insulin	7.4
Cho et al[20]	MODY	Homozygous c.575G>a	Korean	No	22	Male	25.3	13.8	NA	NA	NA
Abreu et al[24]	MODY	Heterozygous c.491G>A	Brazilian	Yes	32	Female	21.6	NA	-	Insulin	NA
			Brazilian	Yes	56	Female	29.48	11.3	-	Metformin and gliclazide	NA
			Brazilian	Yes	49	Female	23.61	6	-	Metformin	NA
Schmidt et al[21]	Ketosis-prone diabetes	Heterozygous c.109C>T	African	No	38	Male	28.4	> 14	-	Insulin	7.0
Mauvais-Jarvis et al[26]	Ketosis-prone diabetes	Homozygous R133W	West African	Yes	47	Male	29.1	13.8	-	Drugs	6.6
			West African	Yes	22	Male	18.5	12.2	-	Drugs	5.1
			West African	Yes	38	Male	28.3	14.1	-	Insulin	6.2
			West African	Yes	20	Male	26.5	12.5	-	Insulin	7.3
		Heterozygous R37W	West African	Yes	39	Male	30.4	11.6	-	Insulin	8.2
Kanatsuka et al[27]	Late-onset diabetic	Homozygous R121W	Japanese	Yes	37	Male	21.5	7.6	-	Insulin	NA
			Japanese	No	71	Male	22.8	7.1	-	Insulin	NA
			Japanese	Yes	71	Female	20.3	6.2	+	Drugs	NA
Shimajiri et al[23]	T2DM	Homozygous R121W	Japanese	No	29	Female	22.2	12.6	-	Insulin	7.3
Present case	T1DM	Heterozygous c.314G>A	Chinese	No	42	Female	31.85	10.3	+	Lifestyle control	7.3

BMI: Body mass index; MODY: Maturity-onset diabetes of the young; NA: Not available; T1DM: Type 1 diabetes mellitus; T2DM: Type 2 diabetes mellitus.

Of these cases, 6 cases[19,22,24,25] with heterozygous PAX4 mutation and 1 case[20] with homozygous PAX4 mutation were diagnosed with MODY, indicating that both homozygous and heterozygous mutations were pathogenic. However, in our case, the patient’s mother had normal blood glucose, possibly because the present site mutation had little pathogenic function, or the mother may progress to diabetes in the future and have longer follow-up needs. The above 6 cases with heterozygous mutations had a family history, while the patient with the homozygous mutation had no family history. Moreover, our case also had no family history. Therefore, it is difficult to determine whether diabetic family history is a characteristic of PAX4 mutation.

Six cases[21,26] were diagnosed with ketosis-prone diabetes, two-thirds of them were homozygous mutation, all were male, and most of them had a family history. One Japanese case of homozygous mutation[23] was diagnosed with type 2 diabetes mellitus (T2DM), and three Japanese cases of homozygous mutation[27] were diagnosed with late-onset diabetes. All of these patients were lean and had no obvious sex and family history differences. Of the 17 cases, only 1 female case with the homozygous mutation had a slightly high level of positive insulin antibody but with a relatively low HbA1c. She was treated with an oral drug and no detailed follow-ups; that case was diagnosed with late-onset diabetes.

Although the c.314G>A mutation has been reported in the dbSNP database, there is no article reporting the specific clinical features of the patients with this mutation nor has it been reported that this mutation is related to LADA. Therefore, our case is significant since it is the first to be reported in China with a mutation site and a high level of autoimmune antibodies. It had a 1-year follow-up to assess the changes in cell function and the progression of the disease.

The literature on the diagnosis of PAX4 mutation with hyperglycemia was controversial. Of the above 17 cases, only 1 case was diagnosed with MODY9, 6 cases were diagnosed only as MODY, and the other cases were diagnosed with ketosis-prone diabetes, late-onset diabetes and T2DM. No case was diagnosed as LADA. While cross-sectional studies found PAX4 gene mutations to be associated with T2DM or ketosis-prone diabetes[21,23,26], population-based studies from China[28], Finland, Hungary[29] and the United Kingdom[30] found no significant association between the PAX4 gene and the risk of developing T1DM. After Biason-Lauber et al[31] proposed that the PAX4 variant 1168C>A was associated with T1DM, Geng et al[32] rejected this point the same year. Mechanically, PAX4 plays a crucial role in the normal differentiation of β cells[9], including promoting the differentiation of stem cells to β cells[11,12], converting mature α cells to β cells[15,16] and maintaining β cell survival and proliferation[13,14]. Therefore, in our case, we considered that the heterozygous mutation in the PAX4 gene might facilitate cell function decline, which coupled with autoimmune antibody destruction accelerates the progression of diabetes. However, this hypothesis also depends on the outcome of her mother’s follow-up.

According to the treatment, in cases with mutations in the PAX4 gene, 9 patients were treated with insulin (52.9%) and 6 patients with oral medication (35.3%). Liraglutide, an incretin hormone that can increase glucose-stimulated insulin secretion, has also been demonstrated to promote β cell proliferation, reduce apoptosis[33,34] and improve β cell function in high-lipid environments by activating the PI3K/Akt pathway[35]. For obese T1DM patients, clinical trials have demonstrated that liraglutide can improve blood glucose, stimulate lipid oxidation and increase thermogenesis while maintaining lean body mass[36]. In T1DM patients with residual islet function, adjuvant therapy with liraglutide has also been proven to reduce HbA1c levels, reduce insulin requirements and increase C-peptide levels[37-39]. We finally added liraglutide to control blood glucose levels and was effectively controlling the patient’s glucose levels at the last follow-up.

CONCLUSION

In this report, we discovered a heterozygous mutation in PAX4 (c.314G>A, p.R105H) that can coexist with LADA and does not appear pathogenic to MODY9 but may facilitate the progression of LADA. Further functional experiments are needed to confirm this in future.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the patient and family members that agreed to participate in this study.