Mycobacterium avium causes infections in immunocompromised individuals. Recurrent infection with this organism has been associated with a deletion at the 818 residue of the interferon-gamma receptor (IFN-gammaR). This mutation produces a truncated receptor without an intracytoplasmic tail, resulting in diminished signaling. We describe a substitution at the 832 residue of the IFN-gammaR causing a similar truncated receptor in a 7-year-old girl with recurrent M avium osteomyelitis.