Acute intermittent porphyria: studies of the severe homozygous dominant disease provides insights into the neurologic attacks in acute porphyrias.

Background: Acute intermittent porphyria (AIP), due to half-normal hydroxymethylbilane synthase activity,is characterized by acute life-threatening neurologic attacks whose etiology remains unclear. To date, only 3 patients confirmed to have homozygous dominant AIP (HD-AIP) have been described (hydroxymethylbilane synthase genotypes R167Q/R167Q and R167W/R173Q).

Objective: To investigate the genetic, biochemical, clinical, and neuroradiologic features of a severely affected infant with HD-AIP.