POLYCLONAL B-CELL LYMPHOCYTOSIS WITH FEATURES RESEMBLING HAIRY-CELL LEUKEMIA JAPANESE VARIANT

Polyclonal B lymphocytosis was found in four patients having clinical and hematologic features resembling those of hairy cell leukemia (HCL) . All four patients were women between 37 and 67 years of age, Three p atients had splenomegaly. Lymphadenopthy was absent or slight, Persist ent lymphocytosis was seen in all the patients, and anemia and/or thro mbopenia was observed in three of the patients. Abnormal lymphocytes h ave long microvilli and prominent membranous ruffles on their surfaces . Bone marrow aspirates and biopsy specimens showed increased numbers of abnormal lymphocytes with round nuclei and abundant pale cytoplasm. Although these findings were similar to those of HCL, studies of 1g g ene rearrangements and expression showed the polyclonal proliferation of B cells. We called this new disease hairy B-cell lymphoproliferativ e disorder (HELD). All four patients exhibited a polyclonal increase i n serum IgG. The morphology of the cells in HELD was more similar to t hat of leukemia cells of a variant form of HCL (HCL-Japanese variant) than to typical HCL cells, The surface IgG(+), CD5(-), CD11c(+), CD22( +), CD24(-), CD25(-) phenotype and the weak tartrate-resistant acid ph osphatase activity in the cells were identical to those of HCL cells o f the Japanese variant, Our findings suggest that the B cells in HELD are the nonmalignant counterpart of leukemic B cells in HCL-Japanese v ariant. (C) 1997 by The American Society of Hematology .