A novel 3-base deletion (IVS3+2_4delTGG) of the hydroxymethylbilane synthase gene in a Brazilian patient with acute intermittent porphyria

Acute intermittent porphyria (AIP, OMIM 176000) is an autosomal dominant metabolic disease caused by mutations in the gene encoding hydroxymethylbilane synthase (HMBS; EC 4.3.1.8; formely named porphobilinogen deaminase, PBGD), mapped to chromosome 11q23.3. We describe a novel mutation of the HMBS gene, a de novo 3-base deletion in the splicing donor site of intron 3 (IVS3+2_4delTGG) in a woman affected by AIP. RT-PCR analysis revealed an abnormal HMBS mRNA, compatible with exon 3 skipping.