Nontuberculous mycobacterial infection following cat scratch in the setting of topical steroid use

Infections due to nontuberculous mycobacteria (NTM) are caused by mycobacterial species other than Mycobacterium tuberculosis, M. leprae, and M. bovis. Patients who are immunocompromised have increased susceptibility to pulmonary, lymphatic, and skin infections by these pathogens. We present a case of a 78-year-old male who presented to dermatology with a left dorsolateral hand infection after sustaining cat scratches in the setting of topical steroid therapy for suspected pyoderma gangrenosum. A shave biopsy of the lesion showed granulomatous dermatitis and associated acid-fast bacilli, while tissue culture grew Mycobacterium chelonae. This case demonstrates cat scratches as an uncommon risk factor for cutaneous NTM disease. Although an association between cat scratches and human NTM infections has only been reported in two previous cases, it must be considered in cases of unusual and persistent cutaneous lesions, especially in immunocompromised patients, even those with only local immunosuppression from topical agents.