Disseminated Mycobacterium avium Complex Infection in a Patient with Autoantibody to Interferon-γ

抄録

A 54-year-old man was admitted to our hospital because of intermittent high fever, general malaise, cough and body weight loss after he had been examined and treated at the former hospital for 3 years without a definitive diagnosis and effective therapy. Bacterial examination on admission revealed Streptococcus pyogenes in peripheral blood, bone marrow aspirates and pleural effusion. Furthermore, Mycobacterium avium complex (MAC) was detected in sputum, gastric juice, bone marrow liquid, pleural effusion by acid-fast bacillus culture or polymerase chain reaction (PCR). Biopsy of the neck lymph node showed multiple granulomas and the presence of acid-fast bacilli. Administration of ABPC/SBT and later CLDM resulted in disappearance of Streptococcus pyrogenes after 2 weeks. We suspected of generalized immunodeficiency that might underlie the severe bacteremia/osteomyelitis and disseminated MAC infection. We tested interferon (IFN)-γ production of peripheral blood mononuclear cells (PBMC) of the patient after phytohemagglutinin (PHA)-stimulation and found that these cells produced no or undetectable levels of IFN-γ in the presence of autologous plasma while produced almost normal levels of IFN-γ in the presence of healthy donor's plasma. Since this neutralizing activity was co-purified in the IgG fraction, the immunodeficient state of the patient seemed to be caused by autoantibody to IFN-γ. As far as we know, this is the first report of a Japanese case of disseminated MAC infection presumably due to autoantibody to IFN-γ.