Mycobacterium genavense is a recently defined fastidious organism that
has been identified as a cause of disseminated infection in patients
with AIDS. We report the cases of two patients who had advanced AIDS a
nd a clinical syndrome of fever, anorexia, abdominal pain, diarrhea, a
nd weight loss. In addition, splenomegaly and lymphadenopathy were pro
minent in both cases, and in one patient's case radiographic findings
were suggestive of splenic abscesses. Mycobacteria isolated from speci
mens of blood and bone marrow grew in liquid media but not on solid me
dia. The results of DNA probe tests for Mycobacterium tuberculosis and
Mycobacterium avium complex were false-positive for both patients. Af
ter treatment of the broth cultures to lyse red blood cells, the resul
ts of DNA probe tests were negative for these pathogens. Amplification
and sequencing of 16S rRNA with use of the polymerase chain reaction
indicated that the mycobacterial isolates from both patients had seque
nces identical to those previously reported for M. genavense. One pati
ent survived 5 months after diagnosis, the other 2 months after diagno
sis; only one patient responded (transiently) to antimycobacterial che
motherapy.