RED CELL (RBC) GLUCOSE PHOSPHATE ISOMERASE DEFICIENCY (GPI): CLINICAL AND LABORATORY EVIDENCE OF INCREASED BLOOD VISCOSITY

Abstract

GPI deficiency is the 3rd most common RBC enzyme defect and results in severe chronic hemolytic anemia. A 9 year old developed priapism six years after splenectomy had improved his unexplained hemolytic anemia. RBC studies showed: Hgb. 10 gm%, reticulocytes 20%, 51Cr t½−4 days, autohemolysisnormal; glucose utilization, lactate production, and 2,3 DPG were normal for cell age. GPI activity was 15% and fell to 4% of normal on exposure of hemolysate to 50°C for 10′. The proportion of 14CO2 from glucose-1-14C and glucose-2-14C in patient RBC's at rest and after stimulation with 2 mM methylene blue was normal indicating glucose-2-14C was capable of recycling past GPI to re-enter the hexose monophosphate shunt. Thus, the GPI deficiency did not inhibit reversed flow of glucose-2-14C. However, phase microscopy of 1% suspensions of patient RBC's in normal saline (NS) revealed 10 to 15% echinocytes. Filtration of 1% suspensions of patient RBC's in Tris-NS through 3 micron pore polycarbonate membranes was impaired at pH 7.4 and ceased at pH 6.8. These studies suggest that despite apparently normal glycolysis, GPI RBC's have decreased filterability at physiologic pH and are totally impeded by severe acidosis. This likely accounts for the splenic sequestration and priapism observed in this patient.