Hairy Cell Leukemia and Bone Pain.

Hairy cell leukemia is a relatively rare but distinct B-cell lympho-proliferative disorder of the blood, bone marrow, and spleen that accounts for only 2% of all adult leukemia cases. The median age at presentation is 50-55 years, with a 4:1 male to female predominance. Although considered uncommon, a number of unusual clinical presentations have been noted in the literature, including the presence of peripheral lymphadenopathy, lytic bone lesions, skin involvement, organ involvement, and central nervous system involvement. Unlike the clinical management of other hematologic malignancies, no current system is used to stage hairy cell leukemia.