[Hairy cell leukemia and Mycobacterium malmoense infection].

We describe a patient with hairy cell leukemia and protracted fever. The patient's condition deteriorated during treatment with alfa Interferon 2b, and his fever persisted. A slight widening of the upper mediastinum appeared after 2.5 months. Mediastinoscopy with lymph node biopsy revealed granulomatous infiltrates with acid-fast bacilli. Cultures of the lymph node material later showed growth of Mycobacterium malmoense. The patient was treated with rifampicin, doxycycline, etambutol and cycloserin for sixteen months and remains afebrile and is gaining weight. His general condition is still improving. An aggressive diagnostic approach is necessary in febrile patients with hairy cell leukemia.