Abstract
This report describes a black family in which two distinct structural defects of alpha spectrin were inherited singly and in combination. The propositus, who has a poikilocytic hemolytic anemia that shares many of the features of hereditary pyropoikilocytosis (HPP) or homozygous elliptocytosis, is a compound heterozygote for both the spectrin alpha 1/65 and spectrin alpha 1/50a defects as demonstrated by electrophoretic analysis of spectrin tryptic fragments. The spectrin alpha 1/65 defect alone was found in his mother and sibling, while the spectrin alpha 1/50a defect was present in the father and another sibling. The red cell spectrin content was normal in all family members. The functional consequences of inheritance of these two spectrin defects were compared with those found in an unrelated patient with classic HPP who had the alpha 1/50a spectrin defect and was spectrin deficient as well. Prolonged incubation at 37 degrees C resulted in striking budding, fragmentation, and sphering of classic HPP red cells but only minimal changes in propositus cells. The percentage of spectrin dimers was increased tenfold in classic HPP, sevenfold in the propositus, and threefold in other family members. Mechanical stability of erythrocyte ghosts, measured by ektacytometry, was reduced severely in both classic HPP and in the propositus, but only moderately in other family members. Thus, co-inheritance of two alpha spectrin defects can result in a poikilocytic hemolytic anemia milder than that usually found in HPP. The greater clinical severity of HPP may be a consequence of the presence of spectrin deficiency, a finding absent in the propositus.
