[Hereditary erythrocyte pyruvate kinase abnormality: another kindred from Aargau Canton]

A Swiss family with abnormal red cell pyruvate kinase is described. In two new-born siblings the red cell defect was responsible for marked hyperbilirubinemia. At the present time both children have compensated hemolysis and are clinically healthy. The abnormal enzyme is unstable and has a decreased Hill coefficient and a decreased substrate affinity. It is different from two other enzyme variants found in the same area.