Toxoplasmosis in hairy-cell leukaemia.

Toxoplasma serology was performed in 28 patients with hairy-cell leukaemia and was positive in eight patients (29%). In two patients (7%) reactivated toxoplasmosis was proven by either isolation of Toxoplasma gondii or by significant antibody titre rise with generation of specific IgM-antibodies. In four patients (14%), a clinical diagnosis of active toxoplasmosis was based on signs and symptoms, serologic tests, and response to specific treatment. The high proportion of patients in which active toxoplasmosis was proven or probable (six; 21%) may be related to the presence of severe monocytopenia. In patients with hairy-cell leukaemia developing fever of unknown origin and myositis, toxoplasma serology should be performed, particularly because treatment of active toxoplasmosis usually is successful.