Acute Hepatic Porphyria

Excerpt

The porphyrias are a set of metabolic disorders, each representing a defect in one of the eight enzymes in the heme biosynthetic pathway that results in the accumulation of organic compounds called porphyrins. This leads to the clinical and biochemical profile typical for each porphyria. Hepatic porphyrias are those in which the enzyme deficiency occurs in the liver. Hepatic porphyrias include acute intermittent porphyria (AIP), variegate porphyria (VP), aminolevulinic acid dehydratase deficiency porphyria (ALAD), hereditary coproporphyria (HCP), and porphyria cutanea tarda (PCT).

These conditions are distinct but have in common the accumulation of heme precursors. For acute porphyrias, which primarily affect the nervous system, the cause of symptoms seems to be the increased production of neurotoxic precursors. With chronic porphyrias, which primarily have skin manifestations, the cause of symptoms seems to be the buildup of photosensitizing porphyrins in the skin. Some types of porphyrias can have both neurological and cutaneous expressions. The treatment is the administration of intravenous hemin to prevent the progression of the symptoms. Liver transplantation (LT) is reserved for patients with life-threatening acute attacks or progression of symptoms despite hemin therapy.