Uroporphyrinogen decarboxylase deficiency in hepatoerythropoietic porphyria: further evidence for genetic heterogeneity.

Catalytic and immunoreactive erythrocyte uroporphyrinogen decarboxylase was measured in a woman with hepatoerythropoietic porphyria (HEP). The uroporphyrinogen decarboxylase activity was 24% of the mean value for normal controls and the concentration of the immunoreactive enzyme (106 ng/mgHb), measured with the rocket immunoelectrophoresis technique, did not differ from that of healthy controls. Consequently, catalytically inactive, cross-reactive immunological material (CRIM) was present, and the patient was CRIM-positive. This enzyme activity and immunoreactive enzyme concentration differs from those for previously known HEP patients, and represents a new mutation, evidence for heterogeneity in inherited uroporphyrinogen decarboxylase deficiency.