Hairy cell leukemia: association with disseminated atypical mycobacterial infection.

The cases of four patients with hairy cell leukemia and disseminated atypical mycobacterial infection (three with M. kansasii and one with M. intracellulare) are reported. These four patients were from a population of 38 patients with hairy cell leukemia evaluated at three institutions; there was an incidence figure of 10.5%. Despite infection with very drug-resistant strains, two patients showed marked clinical improvement following aggressive multiple drug therapy. Such infection should be suspected in a patient with hairy cell leukemia who has persistent fever without an obvious source. Tissue biopsy usually led to diagnosis; urine cultures were also positive in two patients.