A 49-year-old male homosexual patient with AIDS was hospitalized in April 1996 with chronic diarrhea. He had a history of pulmonary pneumocystosis and cryptococcal meningitis. Although blood and stool specimens revealed the presence of acid-fast bacilli, cultures (Bactec, radiometric method, Becton Dickinson Diagnostic Instrument Systems, Sparks, Maryland) remained negative. Treatment with clarithromycin (1 g/d) and ethambutol (1200 mg/d) was instituted under the hypothesis that the patient had Mycobacterium avium complex infection.

The patient was admitted again in June 1996 with abdominal pain, diarrhea, fever, and weight loss. Physical examination showed multiple swelling and painful cutaneous nodules on the abdomen and the tops of the limbs. Liver and spleen were normal. Body temperature was 39°C. Laboratory test results included a hemoglobin level of 6.4 g/dL, an alkaline phosphatase level of 1200 U/L, and a CD4 cell count of 6 cells/mm³. Computed tomography revealed abdominal lymph nodes. Duodenal biopsy showed histiocytic infiltration with acid-fast bacilli. Cutaneous biopsy showed granulomas with diffuse lymphocytic and histiocytic infiltration; acid-fast bacilli were seen on Ziehl-Neelsen stain. Rifampicin, 600 mg/d; isoniazide, 300 mg/d; and pyrazinamide, 1500 mg/d, were added to clarithromycin and ethambutol. Cutaneous lesions and abdominal pain resolved, but weakness and fever persisted. In October 1996, identification of the mycobacterial isolate by polymerase chain reaction restriction analysis of the hsp65 gene revealed M. genavense. No other mycobacterial strain was isolated. Treatment was changed to rifabutin, 450 mg/d; clarithromycin, 1 g/d; and ciprofloxacin, 1500 mg/d. The patient's condition deteriorated, with weight loss and recurrent anemia; the patient died in January 1997 without relapse of cutaneous lesions.

In 1990, Hirschel and colleagues isolated M. genavense for the first time in a patient with AIDS [1]. Since 1990, many cases have been reported. The more frequent signs and symptoms of infection with this organism are fever, weight loss, diarrhea with abdominal pain, hepatosplenomegaly, anemia, and pancytopenia [2]. No subcutaneous nodules have been reported with M. genavense infection. The nontuberculous mycobacteria responsible for cutaneous disease include M. marinum, M. fortuitum, M. chelonae, M. avium complex, and M. haemophilum [3]. In patients with AIDS, M. avium complex, M. fortuitum, and M. haemophilum are the most frequent agents of cutaneous infections [4]. Mycobacterium genavense must be added to this list.

The best treatment for M. genavense remains unknown, but clarithromycin is associated with clinical improvement and clearance of bacteremia [5]. Because of the low frequency of these infections, clinical trials are difficult to conduct to determine the best treatment. Diagnosis of M. genavense infection is difficult because of the fastidious growth requirements of the species. It should be suspected in patients with positive smears for acid-fast bacilli and no or poor growth of the organism. Frequency of M. genavense infection is probably underestimated because of difficulties with cultures. This organism may be the agent of cutaneous disease in patients with AIDS.