Marine Develops Chronic Right Knee Granuloma After Initial Injury at The Basic School

With skin lesions that have failed previous treatments, consideration for an atypical mycobacteria, specifically Mycobacterium marinum, infection should be suspected. Importance of the history cannot be stressed as this is a clue that the patient may have been inoculated and infected in the field environment. A marine with chronic right knee plaque for 3 yr that first appeared after a field exercise at The Basic School but worsened despite treatment with clindamycin, TMP-SMX, and incision and drainage in 2012. Examination revealed a 4 × 4 cm pink, pearly, scaly plaque with scabbing. Deroofing caused puncta to bleed and suppurate. Empiric therapy with doxycycline topical fluocinonide were initiated. Histopathological findings showed dermal fibrosis, granulomatous inflammation, and overlying epidermal inflammation and hyperplasia. Sections also revealed scattered admixed non-necrotizing granulomata. Initial stains, tissue and wound cultures were negative. Acid-fast bacilli broth and smear culture with growth after 4 wk, growing M. marinum. Doxycycline was continued for 2 more months. Mycobacterium marinum is a nontuberculous mycobacterium responsible for skin infections. Sources of infections usually are non-chlorinated water. Infections are rare, an estimated annual incidence of 0.27 cases per 100,000 patients, within the USA and do not cause significant morbidity in immunocompetent patients. Initial M. marinum infections can be mistaken as methicillin resistant Staph aureus infections in the active duty population. If the infection recurs or does not resolve with methicillin resistant Staph aureus-targeted antibiotics, consider cultures specific to acid-fast bacilli and keep in the differential until long term culture results are obtained.