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Gene analysis in hemolytic anemia has been reported recently. It is now recognized that inherited molecular defects of red blood cell membrane proteins have at least five phenotypes. The recent cloning of the G-6-PD gene has given us an entirely new perspective on the population genetics of G-6-PD deficiency and provided new and useful diagnostic tools. Prenatal diagnosis of thalassemia has been possible. Deficiency of the GPI anchor protein may be caused by a somatic mutation of the PIG-A gene in paroxysmal nocturnal hemoglobinuria.

A 19 years old male admitted to our hospital with fever, abdominal pain in May 1991. Physical examination revealed anemia, jaundice and marked splenomegaly. Severe pancytopenia with macrocytic hyperchronic anemia was noted along with elevated LDH and reduced serum folate. Blood smear showed nucleated RBCs, but only few microspherocytes. Bone marrow showed erythroid hyperplasia with remarkable megaloblastic changes. Megaloblasts were negative for PAS stain. Chromosome analysis revealed normal karyotype. Erythroleukemia was suspected initially, but his general condition as well as hematological data improved following 10 units of RBC transfusion. Following brief folic acid supplements, numerous microspherocytes became evident, typical osmotic fragility test revealed a pattern for hereditary spherocytosis. These observations led us to the diagnosis of hereditary spherocytosis complicated by megaloblastic anemia due to folate deficiency. As he developed folate deficiency again 10 months later, splenectomy were performed. The anemia improved after splenectomy.

We developed a simple and quantitative method for determination of erythrocyte osmotic fragility, which is based on a logarithmic linearization of osmotic fragility curve and a calculation of three parameters, that is, C50 (the osmolarity causing 50% hemolysis), beta (the slope of the curve) and H (% hemolysis before treatment). By making use of personal computer program, calculation of the parameters and print-out of reports are automated. As the results, it takes only 30 min to finish all procedure. This method is very useful particularly for the laboratory screening of hereditary spherocytosis.

We report a Childhood case of hereditary spherocytosis (HS) first diagnosed upon the development of aplastic crisis. A 6-year-old boy presented with fever and anemia. Although there was neither icterus nor splenomegaly at first, mild icterus and splenomegaly gradually developed with improvement of anemia. The diagnosis of HS was made on the basis of the presence of numerous spherocytes on the peripheral smear, increased osmotic fragility and the auto-hemolysis test result. The severe anemia in the early course with a marked decrease in the bone marrow erythroid cells and the absence of icterus and splenomegaly indicate that it was due to aplastic crisis. In the virological study, anti-human parvovirus (HPV) antibody titers were increased: the values of anti-HPV IgM were high and those of anti-HPV IgG were suddenly elevated. We thus considered that this HS case developed aplastic crisis by HPV infection.