Acute attacks are associated with the accumulation of the heme pathway intermediates that include porphyrin precursors ALA and consequently PBG from the induced activity of hepatitis ALAS1 and partial hepatic heme deficiency, often in response to the induction of hepatic cytochrome P450 by drugs and other factors. Porphyrias also classified as hepatic porphyrias are AIP, variegate porphyria (VP), hereditary coproporphyria (HCP), and porphyria cutanea tarda (PCT). The gene discussed is ALAS1; the disease is porphyria.