Disseminated Mycolicibacter arupensis and Mycobacterium avium co-infection in a patient with anti-interferon-γ neutralizing autoantibody-associated immunodeficiency syndrome.

BACKGROUND: Disseminated infections of Mycolicibacter arupensis, a slowly growing nontuberculous mycobacteria (NTM) which causes synovitis, osteomyelitis, or pulmonary infections have rarely been reported. We report a case of disseminated M. arupensis and Mycobacterium avium co-infection in a patient with anti-interferon (IFN)-γ neutralizing autoantibody-associated immunodeficiency syndrome. CASE PRESENTATION: A 68-year-old Japanese male without human immunodeficiency virus infection was referred with complaints of persistent low-grade fever, arthralgia of the upper limbs, and weight loss of 10 kg. Cervical and mediastinal lymphadenopathies as well as a nodular opacity in the right lung were detected, and biopsy specimens of the cervical lymph node yielded M. arupensis without evidence of malignant cells. M. arupensis was also detected in sputum and peripheral blood. Computed tomography (CT) revealed deterioration of the right supraclavicular lymphadenopathy with internal necrosis and multiple low-density splenic lesions. Bone marrow and aspirates from the cervical lymph node collected at initiation of treatment yielded M. avium. The presence of anti-IFN-γ neutralizing autoantibodies was detected, leading to a diagnosis of co-infection of M. arupensis and M. avium with anti-IFN-γ neutralizing autoantibody-associated immunodeficiency syndrome. Post initiation of treatment with clarithromycin, ethambutol, and rifabutin, his fever declined, and his polyarthritis resolved. He developed disseminated varicella zoster during treatment; however, a follow-up CT scan six months after treatment revealed improvement of the lymphadenopathies, consolidation in the right lung, and splenic lesions. CONCLUSION: This is the first report of disseminated M. arupensis and M. avium co-infection in a patient with anti-IFN-γ neutralizing autoantibody-associated immunodeficiency syndrome.