[Enzyme deficiency of erythrocytes in human porphyria]

Hereditary enzyme deficiency in porphyrias can be recognized in blood cells. In the red cell four enzymes of heme biosynthesis can be detected: porphobilinogen synthase (delta-aminolevulinic acid dehydrase), uroporphyrinogen synthase, cosynthase, and decarboxylase. A decrease of porphobilinogen synthase is observed in lead intoxication and in a new type of hereditary acute porphyria with nearly total enzyme deficiency in the homozygous state with a residual activity of 1-2% of controls. In another recessive condition, congenital erythropoietic porphyria, the deficient uroporphyrinogen cosynthase shows an activity between 1 and 20%. Acute intermittent porphyria is characterized by diminished uroporphyrinogen synthase which allows the recognition of gene carriers in red cells. In the genetic type of porphyria cutanea tarda triggered by alcohol, oral contraceptives, and liver damage the uroporphyrinogen decarboxylase is decreased to about 50%. In hepatoerythropoietic porphyria, a homozygous variant of porphyria cutanea tarda, decarboxylase activity was found below 10% of controls. With exception of congenital erythropoietic, hepatoerythropoietic porphyria, and lead poisoning enzyme deficiencies of porphyrin metabolism in red cells do not lead to anemia.