Diagnosis and therapy of acute intermittent porphyria.

The porphyrias are a group of disorders caused by deficiencies in the activities of the enzymes of the heme biosynthetic pathway. As a result, abnormally elevated levels of porphyrins and/or their precursors, e.g. delta-aminolevulinic acid and porphobilinogen are produced in excess, accumulate in tissues, and are excreted in urine and stool. Two cardinal symptoms of the porphyrias are cutaneous photosensitivity and neurologic disturbances. Acute intermittent porphyria is the most important form of hepatic porphyria because of its frequency and severe clinical symptoms.