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Mycobacterium kansasii in a patient with hairy cell leukaemia

A 70-year-old man was referred for the investigation of fevers, sweats and neutropenia. Full blood count showed a haemoglobin concentration 120 g/l, white blood cell count (WBC) 2Æ1 · 10/l, neutrophils 0Æ9 · 10/l, monocytes 0Æ0 · 10/l and platelets 195 · 10/l. Blood film, bone marrow biopsy and immunophenotyping confirmed hairy cell leukaemia (HCL). A computerized tomography (CT) scan showed normal lung fields, small volume mediastinal and right hilar lymphadenopathy (1Æ5 cm) and a bulky spleen. He was initially treated with alpha interferon to increase his WBC but this was discontinued due to deranged liver function tests. Subsquently, because he was still neutropenic, four weekly infusions of rituximab (375 mg/m) were given. A few weeks later, he was admitted with neutropenic sepsis, which was unresponsive to broad-spectrum antibiotics and antifungals. A bone marrow biopsy (left) showed complete remission but non-caseating granulomas. A CT chest scan revealed bilateral pleural effusions, enlarged mediastinal and right hilar lymph nodes and a pulmonary infiltrate in the right apex. The findings were consistent with infection and highly suspicious of tuberculosis. A bronchoscopy with bronchial washings and aspiration of pleural fluid was performed, but unfortunately he died acutely of severe sepsis. Post mortem examination (right) showed extensive central necrosis of a mediastinal node. Ziehl-Neelson staining revealed numerous acid-fast bacilli of atypical morphology (right). Subsequently the pleural fluid and bronchial washings confirmed the diagnosis of Mycobacterium kansasii infection. Mycobacterium kansasii is an environmentally acquired microorganism, which usually causes infection in patients with pre-existing chronic lung disease or those with immunodeficiency. This case demonstrates that environmental mycobacteria can cause acute infection in patients with haematological conditions such as HCL who are severely immunosuppressed. Therefore one should investigate these patients with pyrexia of unknown origin for evidence of atypical mycobacterial infection.