Osmosis video - Acute intermittent porphyria

Acute intermittent porphyria is a rare genetic disorder in which there is a deficiency of a heme biosynthetic enzyme called hydroxymethylbilane synthase (HMBS). Without HMBS, the synthesis of heme is impaired, which results in the accumulation of metabolites delta-aminolaevulinic (ALA), and porphobilinogen (PBG), which are potentially toxic.

Signs and symptoms of acute intermittent porphyria usually begin between the ages of 20 and 40. They can include abdominal pain, vomiting, constipation, seizures, mental confusion, signs of peripheral neuropathy, and dark urine.