We studied the clinicopathological features of eight patients in whom a
non-tuberculous mycobacterium was unexpectedly isolated from osteoarticular
material obtained at operation. Three distinct types of infection with
non-tuberculous mycobacteria were found: tenosynovitis, synovitis, and
osteomyelitis. Tissue specimens from these sites showed a spectrum of
pathological findings, including (1) virtually no inflammation, (2) mild to
severe non-specific chronic inflammation, (3) granulomas without necrosis,
and (4) caseating epithelioid granulomas that were indistinguishable from
those of tuberculosis. In six patients the infection responded well to
adequate surgical excision alone. In the remaining two the infection
responded to surgical intervention and antituberculous therapy.