[Demonstration of hereditary enzyme defect in coproporphyria]

We measured lymphocytes Coproporphyrinogen III Oxidase activity in 17 subjects with hereditary coproporphyria. The mean activity was about 50% of that in lymphocytes from normal subjects. This finding suggests that decreased coproporphyrinogen III oxidase activity reflects the primary genetic defect in Hereditary Coproporphyria. The technique described allows easy detection of asymptomatic carriers.