Fish tank granuloma--a frequently misdiagnosed infection of the upper limb

Five patients attended the accident and emergency (A&E) department with fish tank granuloma caused by an infection with Mycobacterium marinum. All patients had forearm symptoms which were initially misdiagnosed. They were later recognised by the presence of superficial cutaneous lesions in a sporotrichotic distribution. Definitive diagnosis was confirmed by the histological appearances of a biopsy and or culture of the organism. All patients responded to oral minocycline and had uncomplicated recoveries once the diagnosis was established. A&E doctors need to be aware of the possible diagnosis of fish tank granuloma especially when treating forearm infections which have been resistant to antibiotics.