Coexistence of Congenital Red Cell Pyruvate Kinase Deficiency and Hereditary Stomatocytosis.

We describe a case of chronic hemolytic anemia due to the co-presence of pyruvate kinase (PK) deficiency and Hereditary Stomatocytosis (HSto). The propositus was a 30 years old adopted male with no known family history; he had severe neonatal jaundice requiring exchange transfusion, followed by a life-long history of moderate to severe chronic hemolytic anemia (Hb 7–10 g/dL), with jaundice and splenomegaly. At the age of 6 months hemoglobin screening was made and a beta trait was found. At the age of 20 splenectomy and cholecystectomy were performed. Surgery resulted in an increase of 1.5 g/dL in haemoglobin, and in a conspicuous rise of reticulocytes (from 125×10⁹/L to 562×10⁹/L). Two thrombotic events occurred thereafter, the former 6 days after surgery, and the latter two years later, during a toxoplasmosis infection. At the time of the study Hb was 10.8 g/dL, MCV 82.2 fL, reticulocytes 562×10⁹/L, unconjugated bilirubin 2.19 mg/dL, LDH 335 U/L, haptoglobin <20 mg/dL, serum ferritin 342 ng/mL and transferrin saturation 71%. The peripheral blood smear examination showed the presence of echinocytes (13%), stomatocytes (11%), acantocytes (10%), schistocytes (7%), elliptocytes (6%), spherocytes (4%), target cells (4%) and a few erythroblasts. Erythrocyte osmotic fragility was decreased; screening test for unstable hemoglobins and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of red cell membrane gave normal results. The study of the most important red cell enzymes revealed reduced PK activity (6.0 UI/gHb, normal range 11.1–15.59 UI/gHb) and thermal stability (43%, normal range 57–100%). Direct sequencing of PK-LR gene showed a compound heterozygosity for mutation 1456T (Arg486Trp) and the new variant −73g>c. Mutation −73g>c occurs in the most proximal of the four GATA motifs in the R-type promoter region and possibly result in a decrease of mRNA synthesis, as already reported for the variant −72a>g (Manco et al, 2000). Molecular analysis of HFE gene showed heterozygosity for H63D mutation. The history of post splenectomy thrombosis and the presence of stomatocytes in peripheral blood smear prompted us to investigate for the coexistence of hereditary stomatocytosis. The determination of plasma potassium and sodium concentration revealed an increase in intracellular sodium (16.3 mmol/LRBC, reference range 5.0–12.0) and a decrease in intracellular potassium (74.73 mmol/LRBC, reference range 90–103), suggestive for a diagnosis of dehydrated HSto, or hereditary xerocytosis. This defect likely accounts for the thrombophilic state in this case, since HSto is known to be associated with hypercoagulability, particulary after splenectomy.