[The first case in Japan of unstable hemoglobin, Hb Buenos Aires [beta 85 (F1) Phe-->Ser], with parvovirus B19 infection (first case in Japan)].

A 9-year-old girl was admitted to Mie University Hospital June 25, 1992, complaining of fever, skin rash and pallor. Physical examination revealed anemia and hepatosplenomegaly. Laboratory findings showed normocytic normochromic anemia, increased reticulocyte counts and remarkably decreased haptoglobin level. Red blood cells had no morphological abnormality. Bone marrow examination showed erythroid hyperplasia without abnormal cells. Hemoglobin electrophoresis showed an abnormal band. The amino acid structure and sequence of the abnormal hemoglobin was determined to be an unstable hemoglobin, Hb Buenos Aires [beta 85 (F1) Phe-->Ser]. Sequence of genomic DNA and cDNA was compatible to Hb Buenos Aires. Parvovirus B19 infection was thought to have caused severe anemia due to hemolytic crisis in this patient because its IgM antibody was positive on admission. She recovered soon without any treatment and has been followed in the outpatient clinic. Her parents and brother showed no hemoglobin abnormality.