The following enzyme defect causes acute intermittent porphyria

The defective enzyme in acute intermittent porphyria is hydroxymethylbilane synthase (uroporphyrinogen I synthase)ALA and porphyrobilinogen accumulate in body tissues and fluids.It is an autosomal dominant disorder.While most porphyrias are inherited in an autosomal dominant manner, congenital erythropoietic porphyria is inherited in a recessive mode. The defective enzyme in congenital erythropoietic porphyria is uroporphyrinogen III synthase,Harper 30th edition pg: 329