The acute porphyrias.

The porphyrias are a heterogeneous group of rare inborn errors of metabolism caused by inherited enzyme defects in the haem biosynthetic pathway, resulting in overproduction of porphyrins. The porphyrias can be distinguished biochemically but may be difficult to differentiate clinically. Considerable advances have been made in the understanding of the enzymology and molecular biology of the porphyrias. The acute attack of porphyria may be a life-threatening condition, and an understanding of its many precipitating factors, clinical features and management is of importance in a disease with a significant mortality.