Identification of two novel PBGD mutations in acute intermittent porphyria patients accompanying anemia in mainland China

A novel 55-basepair deletion of hydroxymethylbilane synthase gene found in a Chinese patient with acute intermittent porphyria and her family: A case report

RATIONALE

Acute intermittent porphyria (AIP) is caused by hydroxymethylbilane synthase (HMBS) gene mutation.

PATIENT CONCERNS

A Chinese female patient with very typical AIP symptoms of severe abdominal pain, seizures, hypertension, and tachycardia, accompanied with hyponatremia, anemia, and hyperbilirubinemia.

DIAGNOSES

She was diagnosed as AIP based on positive result of urine porphobilinogen and her clinical syndrome.

INTERVENTIONS

The proband was treated with intravenous glucose (at least 250 g per day) for 4 days. HMBS mutation was investigated in this family by Sanger sequencing.

OUTCOMES

A heterozygous mutation of the HMBS gene was identified in the proband and 7 other family members. Genetic sequencing showed a deletion of 55 basepairs (C.1078_1132delGCCCATTAACTGGTTTGTGGGGCACAGATGCCTGGGTTGCTGCTGTCCAGTGCCT) including the stop codon position, leading to frameshift mutation. The mutation has not been documented in current gene databases. Further prediction of mutated protein structure suggests that the mutation is likely to produce prolonged peptide with structural change and less stability.

LESSONS

Physicians should pay attention to AIP attack in patients with suspected symptoms and make use of genetic testing to increase identification of mutated HMBS gene carriers for further preventive strategy.

Whole Exome Sequencing Identified a Novel Heterozygous Mutation in HMBS Gene in a Chinese Patient With Acute Intermittent Porphyria With Rare Type of Mild Anemia

Acute intermittent porphyria (AIP) is a rare hereditary metabolic disease with an autosomal dominant mode of inheritance. Germline mutations of HMBS gene causes AIP. Mutation of HMBS gene results into the partial deficiency of the heme biosynthetic enzyme hydroxymethylbilane synthase. AIP is clinically manifested with abdominal pain, vomiting, and neurological complaints. Additionally, an extreme phenotypic heterogeneity has been reported in AIP patients with mutations in HMBS gene. Here, we investigated a Chinese patient with AIP. The proband is a 28-year-old Chinese male manifested with severe stomach ache, constipation, nausea and depression. Proband’s father and mother is normal. Proband’s blood sample was collected and genomic DNA was extracted. Whole exome sequencing and Sanger sequencing identified a heterozygous novel single nucleotide deletion (c.809delC) in exon 12 of HMBS gene in the proband. This mutation leads to frameshift followed by formation of a truncated (p.Ala270Valfs^∗2) HMBS protein with 272 amino acids comparing with the wild type HMBS protein of 361 amino acids. This mutation has not been found in proband’s unaffected parents as well as in 100 healthy normal control. According to the variant interpretation guidelines of American College of Medical Genetics and Genomics (ACMG), this variant is classified as “likely pathogenic” variant. Our findings expand the mutational spectra of HMBS gene related AIP which are significant for screening and genetic diagnosis for AIP.

Novel A219P mutation of hydroxymethylbilane synthase identified in a Chinese woman with acute intermittent porphyria and syndrome of inappropriate antidiuretic hormone

Acute intermittent porphyria (AIP) is an autosomal dominant metabolic disorder caused by deficiency of the heme biosynthetic enzyme hydroxymethylbilane synthase (approved gene symbol HMBS), also known as porphobilinogen deaminase (PBGD). AIP is characterised by intermittent attacks of abdominal pain, vomiting, and neurological complaints. The highly variable symptomatic presentation of AIP causes confusion with other diseases and results in a high misdiagnosis rate (68% in China) and delayed effective treatments. Based on biochemical and genetic analysis of two Chinese families, a new and a previously reported HMBS mutation were identified in patients with AIP and syndrome of inappropriate antidiuretic hormone (SIADH). The novel HMBS mutation is the 655G>C point mutation (A219P). In addition, the 973C>T point mutation (R325X), which had been previously reported in two Danish families, was identified.

Recurrent porphyria attacks in a Chinese patient with a heterozygous PBGD mutation

We report here the case of a 32-year-old Chinese Han woman who presented with frequent severe abdominal pain, convulsion, numbness and confusion. She also had hypertension, hyponatremia, chronic renal failure, anemia and a high urinary δ-aminolevulinic acid concentration. We identified a heterozygous splicing mutation in intron 11 (IVS11-2A→G) of the porphobilinogen (PBG) deaminase gene (PBGD) in her genomic DNA. This mutation had previously been reported in a North American patient, but was absent from 50 healthy Chinese controls.