[Severe tularaemia mimicking glandular tuberculosis during adalimumab therapy]

Tularaemia is an anthropozoonosis, transmitted by small mammals (hares) and arthropods (ticks, horseflies). The causative agent is Francisella tularensis, a facultatively intracellular Gram-negative bacillus. We report a case of tularaemia in its ulceroglandular form occurring during methotrexate and adalimumab treatment (Humira) for rheumatoid arthritis.

A 58-year-old man with a history of primary tuberculosis receiving adalimumab in combination with methotrexate for rheumatoid arthritis for almost 1 year consulted for a febrile inflammatory plaque on the left leg with a small central necrotic area. An enlarged left inguinal lymph node was present. Doxycycline has previously been prescribed for a tick bite. The lymphadenopathy gradually became enlarged resulting in skin fistulisation. After surgical excision, histopathology revealed epithelioid granulomas accompanied by giant cells and central necrosis. Mycobacterial cultures were negative. Positive tularaemia serology at significant titres suggested a diagnosis of tularaemia, with probable transmission via a tick bite. The diagnosis was confirmed by F. tularensis DNA amplification using PCR on a lymph node biopsy. Doxycycline was continued for a further 6 weeks. One year later, no relapse had occurred.

A febrile adenopathy presenting the histological features of necrotic granulomas in a patient receiving anti-TNF alpha treatment initially suggested reactivation of tuberculosis. However, the history of tick bite and failure to isolate mycobacteria from different tissue specimens prompted screening for a tick-borne disease, finally leading to a diagnosis of tularaemia. We discuss the possible relationship between immunosuppression and the clinical course of this rare infection.