EARLY AGE ONSET OF HAIRY-CELL LEUKEMIA PRESENTING WITH LEUKOCYTOSIS

Hairy cell leukemia (HCL) is an uncommon type of chronic B cell leukem ia mainly affecting middle-aged adults. HCL presenting with pancytopen ia is rare in Japan and a distinct subtype of HCL termed HCL-Japanese Variant is predominantly seen. We describe a HCL patient with unusual presentation. The patient was a 26-year-old male, such early onset of HCL being quite rare. The patient showed leukocytosis with many circul ating hairy cells and cellular bone marrow. These findings were prefer entially seen in HCL-Japanese variant, but, cytomorphologic, cytochemi cal and immunophenotypical studies on the pathologic cells were consis tent with those of typical HCL seen in Western countries. Interferon-c r therapy was very effective in this case. Differentiation of the subt ype of HCL appears to be important for the choice of the treatment. Th e cytological findings were useful for the differential diagnosis of H CL presenting with leukocytosis.