[Congenital hemolytic anemia with erythrocyte thermal instability and defect of spectrin tetrameric polymerization. Study of erythrocyte deformability in a new case of hereditary pyropoikilocytosis using diffraction viscosimetry].
Hereditary pyropoikilocytosis (HPP) is a rare congenital hemolytic anaemia observed so far in patients of black extraction. In many cases, the severity of the anaemia has led to early splenectomy, which uniformly improved the hematological conditions. The disease is characterized by extreme anisocytosis and poikilocytosis with erythrocyte fragmentation. The pathognomonic feature is the abnormal thermal sensitivity of red cells which fragment in vitro at 45-46 degrees C (instead of 49 degrees C in normal subjects). In the case reported here, erythrocyte fragmentation (which appears at 43 degrees C) and increased osmotic fragility are studied using the Ektacytometer. Observation of different erythrocyte fractions isolated by differential centrifugation shows the extreme heterogeneity of the erythrocyte population. Studies of erythrocyte membrane proteins confirm that the disease is related to defective dimer-dimer association of spectrin which is the major membrane skeletal protein. This molecular spectrin abnormality in accounting for the membrane instability is recognized to a lesser degree in the asymptomatic mother. This may be of use in the diagnosis of HPP which is difficult to establish in a transfusion-dependent infant.