Hereditary pyropoikilocytosis and elliptocytosis in a Caucasian family. Transmission of the same molecular defect in spectrin through three generations with different clinical expression.

Hereditary pyropoikilocytosis (HPP) is a severe hemolytic anemia characterized by a material instability of the red cell membrane leading to cell fragmentation. This fragility may be correlated with functional and structural defects of spectrin. Most HPP patients have been black. We now report three HPP patients from a Caucasian family, the proposita and her two maternal uncles. The proposita's mother and daughter presented mild type I hereditary elliptocytosis (HE), while the proposita's father was clinically and hematologically normal. Our studies revealed a defective ability of spectrin to self-associate, resulting in an excess of spectrin dimer in 4 degrees C extracts in the three HPP patients and to a similar extent in HE relatives. Limited tryptic digestion of spectrin showed a molecular variant in the alpha I domain as expressed by a decreased amount of 80,000-dalton peptide with a concomitant increase in the 74,000-dalton peptide. Investigations in the proposita's father revealed no abnormalities of the erythrocyte membrane. The co-transmission of HPP and HE phenotypes in the same lineage might suggest variability in the clinical expression of the same molecular defect and lead us to discuss the hypothesis of a double heterozygosity in HPP patients.