Acute intermittent porphyria (AIP, MIM # 176000) is an autosomal dominant disorder caused by a mutation in the HMBS gene that results in deficiency of the third enzyme in heme biosynthesis, hydroxymethylbilane synthase (HMBS)—also known as porphobilinogen deaminase (PBGD)—and the accumulation of the heme precursors δ-aminolaevulinic acid (δ-ALA) and porphobilinogen (PBG) in the body, resulting in a series of digestive and neuropsychiatric symptoms.[1]. Here, HMBS is linked to autoimmune pancreatitis.