Sweet's syndrome as the presenting symptom of hairy cell leukemia with concomitant infection by Mycobacterium kansasii.

A patient with Sweet's syndrome and leukopenia is reported. Hematological evaluation revealed hairy cell leukemia (HCL). The clinical picture was dominated by persistent fever, which is a common feature of both Sweet's syndrome and HCL. Since fever frequently reflects concomitant infection in HCL, a thorough search for infectious disease was performed. Blood cultures grew Mycobacterium kansasii. The patient recovered after treatment with recombinant interferon-alpha (r-IFN-alpha) and tuberculostatic drugs. Remarkably, the skin lesions completely regressed within 1 week after the start of r-IFN-alpha. In the literature, Sweet's syndrome is rarely mentioned as a feature of HCL. Mycobacterial disease, especially atypical mycobacteria, is relatively often seen in HCL.