Mycobacterium longobardum Infection in the Hand

Mycobacterium longobardum is a slow-growing, nontuberculous mycobacterium that was first characterized in 2012. We report a case of M. longobardum infection in the right middle finger of a diabetic man. He underwent surgery for a presumed diagnosis of an epidermal inclusion cyst. Molecular diagnosis of the surgical specimens demonstrated M. longobardum through RNA polymerase β-subunit encoding gene sequencing. After surgery, the patient was treated with antibiotics and eventually cured of the infection. To the best of our knowledge, this is only the second reported case of a pathogenic M. longobardum infection worldwide and the first such case in the hand. The purposes of this case study are to alert treating providers to consider nontuberculous mycobacterium infection when an inflammatory process persists, discuss signs and symptoms of the disease, and provide general treatment guidelines.