Porphyrias

The porphyrias are a heterogeneous group of metabolic disorders caused by genetic defects of the enzymes involved in heme biosynthesis. The diseases are characterized by excessive accumulation and excretion of porphyrin or porphyrin precursors. The disorders have been classified as cutaneous, hepatic, or neuropsychiatric according to the organ system involved. This review describes the enzymes of the heme biosynthetic pathway along with the clinical features and management of the porphyrias.

Hepatic porphyrias

The porphyrias are metabolic disorders characterized by abnormal heme biosynthesis with excessive accumulation and excretion of porphyrias or porphyrin precursors. Defects in the enzymes of the heme biosynthetic pathway result in porphyria. Several of the disorders have been classified as hepatic because the major site of the biochemical defect has been localized to the liver. This article describes the enzymes of the heme biosynthetic pathway, the clinical features of the hepatic porphyrias and management of the disorders.