Aplastic anemia terminating in hairy cell leukemia. A report of two cases.

Aplastic anemia and hairy cell leukemia (HCL) characteristically present with a pancytopenia, and several reports have described HCL as mimicking aplastic anemia. Usually the bone marrow core biopsy will easily differentiate these entities, as aplastic anemia is hypocellular, and HCL has a mononuclear cellular infiltrate with increased reticulin. In the experience of the author with 67 cases of HCL, two cases have been encountered that clinically and morphologically appeared to be aplastic anemia before terminating in HCL 23 months and 15 months later, respectively. The clinical courses are described for these two individuals. Hairy cell leukemia may not only mimic aplastic anemia, but on rare occasions, aplastic anemia may actually precede hairy cell leukemia.