Acute intermittent porphyria

A rare autosomal dominant inherited disorder characterized by a partial deficiency of porphobilinogen deaminase, which leads to the accumulation of porphyrin precursors in the body.

Most patients remain asymptomatic, but symptoms can be triggered by use of certain drugs or alteration of nutritional status.

The most common presenting features include pain in the abdomen, extremities, back, and chest, tachycardia, hypertension, nausea, vomiting, constipation, and peripheral motor neuropathy.

The pain is neuropathic and not accompanied by inflammation.

Red or brownish urine results from marked increases in urinary excretion of heme pathway intermediates. Porphyrins are reddish and fluoresce when exposed to long-wave ultraviolet light. Porphobilinogen is colorless but degrades on standing to form brownish pigments.

Acute intermittent porphyria (AIP) is a rare genetic disorder characterized by a partial deficiency of porphobilinogen deaminase (PBGD), also known as hydroxymethylbilane synthase, the third enzyme in the heme biosynthetic pathway. As a result, the porphyrin precursors, porphobilinogen (PBG), and delta-aminolevulinic acid (ALA) accumulate in the body. Urinary excretion of ALA, PBG, and porphyrins is increased. Most patients remain asymptomatic with little or no elevation in ALA, PBG, and porphyrins, but the condition can be activated after puberty by some drugs and corticosteroid hormones or by reducing dietary intake.