summary Atypical Mycobacterial Infections of the hand are rare hand infections that are most commonly caused by M. marinum. Diagnosis is made by clinical examination with presence papules, ulcers, and nodules and confirmed with cultures (Lowenstein-Jensen culture agar). Treatment of early disease is oral antibiotics (antimycobacterials). Epidemiology Incidence rare 0.05 per 100,000 annually Demographics often found in marine workers Location hand and wrist are involved in 50% of cases Risk factors immunocompromised host Etiology Pathophysiology incubation average incubation period is two weeks, but can be up to six months average time to diagnosis and appropriate treatment is more than 1 year organisms widely encountered in the environment, but rarely cause human pathology M. marinum most common atypical mycobacterium infection more common in stagnant fresh or salt water (aquariums) M kansasii found in soil M terrae found in soil M. avium intracellulare most common in terminal AIDS patients, but can occur in non-HIV patients Presentation Symptoms cutaneous rash with discomfort Physical exam papules, ulcers, and nodules are common, especially on the hands many times presents with a single nodule that may ultimately spread to the lymph nodes indistinguishable from tuberculous mycobacterial infection Studies Histology granulomas may or may not demonstrate acid-fast bacilli on AFB stain Cultures and sensitivities are key to diagnosis Lowenstein-Jensen culture agar M. marinum incubated specifically at 30 to 32° C M. avium intracellulare incubated at room temperature Differential Herpetic Whitlow Fungal infections Psoriasis Diagnosis Clinical and culture-based diagnosis is made with careful history and physical examination and confirmed with a positive cultures Treatment Nonoperative oral antibiotics indications if diagnosed at early stage medications ethambutol, tetraycline, trimethoprim-sulfamethoxazole, clarithromycin, azithromycin add rifampin if osteomyelitis present Operative surgical debridement + oral antibiotics in combination for 3 to 6 months indications later stage disease use a combination of above medications Prognosis Natural history early presentation includes papules, nodules, and ulcers late presentation may have progressed to tenosynovitis, septic arthritis, or osteomyelitis Morbidity & mortality mortality rate with presence of sepsis is 32%