Acute intermittent porphyria (AIP), the most common form of acute hepatic porphyria, is an autosomal dominant disorder caused by a partial deficiency in the activity of the third enzyme in the heme biosynthesis pathway, hydroxymethylbilane synthase (HMBS), also known as porphobilinogen deaminase (PBGD) (Puy et al., 2010). The gene discussed is HMBS; the disease is autoimmune pancreatitis.