Unusual Cause of a Large Ulcer from Travelling in South America

A 27 year old British man presented with a painless, slowly enlarging ulcer on the lateral aspect of his left knee. The lesion had begun during a wildlife tour in the Pantanal region of Brazil and the Southern Peruvian Amazon. At presentation it measured 11 x 6 cm and was characterised by deeply undermined edges and a dense adherent eschar. It was debrided with larval therapy and then biopsied. Histology revealed numerous, atypical acid-alcohol fast bacilli and inflammation of the dermal tissue with necrosis of the subcutaneous fat. Mycobacterial culture did not yield any significant isolates. Polymerase chain reaction for Leishmania species was negative on two occasions. The patient was subsequently treated with 6 weeks of clarithromycin monotherapy for presumed Mycobacterium marinum infection but the lesion continued to enlarge. In consequence he was referred to the regional Infection and Travel Medicine department. A further diagnostic procedure was performed and the patient commenced on appropriate therapy with subsequent clinical improvement. This condition is rarely seen in South America and this is the first reported case of infection in a traveller returning to the UK.