Acute intermittent porphyria: pathophysiology and treatment.

Acute intermittent porphyria is caused by an inherent error of porphyrin metabolism characterized by a deficiency of porphobilinogen deaminase and increased activity of delta-aminolevulinic acid synthase, key enzymes necessary for the biosynthesis of heme. During an attack patients may have abdominal pain, vomiting, muscle weakness, constipation and neuropsychiatric symptoms. In the majority of individuals the disease remains clinically latent throughout life. Various drugs and chemicals, hormones and nutritional factors predispose to clinical attacks, probably by inducing hepatic delta-aminolevulinic acid synthase. Avoidance of these substances is important in preventing attacks. Screening of family members to detect genetic carriers permits precautionary measures. Management of attacks includes symptomatic therapy, high carbohydrate intake and intravenous administration of hematin.