Novel hydroxymethylbilane synthase gene mutation identified and confirmed in a woman with acute intermittent porphyria: A case report

Figure 1 The color of the patient’s urine sample changed during an acute attack. Sunlight exposure of her urine sample for 1 h turned it from yellow to wine red. A: Yellow; B: Wine red.

Figure 2 Gene sequencing and pedigree of the family. A: DNA sequencing showing the mutation c.648_651+1delCCAGG in hydroxymethylbilane synthase gene in the family members; B: Segregation of mutant alleles of the index patient (Ⅲ.2). Solid symbols represent the overt proband indicated by an arrow, symbols with a dot in the middle represent asymptomatic latent family members carrying the mutation.

Figure 3 Validation of splicing alteration. A: Sequencing analysis minigenes: Top, mutant minigene containing c.648_651+1delCCAGG; bottom, wild-type minigene; B: Reverse Transcription Polymerase Chain Reaction of wild-type or mutant minigenes on agarose gel electrophoresis; C: Minigene construction and splicing pattern; D: Minigene splicing assay: Top, wild-type minigene; bottom, mutant minigene with retention of intron 10.

Figure 4 Bioinformatics analysis. A: ORFfinder software predicted that the novel mutation gene translates a truncated protein (248 amino acids) with the deletion of 113 amino acids; B: The novel mutation in the hydroxymethylbilane synthase (HMBS) gene. The mutation shows that 5 bps (CCAGG) located at the intron and exon junction have been removed, resulting in the deletion of 4 bps of exon 10 and insertion of intron 10 (239 bps). The mutation site is represented by a red box; C: HMBS amino acid residues across different species; D: PredictProtein revealed an obvious difference between wild-type and predicted proteins in the strand and helix regions, exposed and buried regions, disordered regions, protein binding regions, and DNA and RNA binding region.

Figure 5 A timeline of her three pregnancies. She had her first pregnancy and gave birth to a boy in February, 2017; she had a second pregnancy in March, 2018, but had a spontaneous abortion due to an acute attack of acute intermittent porphyria (AIP); she became pregnant for the third time in September, 2018, but had an abortion because of the acute attack of AIP.