Disseminated nontuberculous mycobacterial infection in a patient with IFN-γ neutralizing antibodies and idiopathic CD4 lymphocytopenia: a case report

Abstract

Abstract Background: Disseminated nontuberculous mycobacterial (NTM) infection usually occurs in immunodeficient patients, such as those with acquired immunodeficiency syndrome. However, disseminated NTM diseases have also been reported in immunocompetent patients. Autoantibodies to interferon-gamma (IFN-γ) are known to be involved in disseminated NTM disease, although anti-IFN-γ antibodies are mainly seen in immunocompetent patients rather than those with immunodeficiency. Here, we report a rare case of disseminated NTM that was positive for anti-IFN-γ antibodies in a patient with idiopathic CD4 lymphopenia. Case presentation: A 64-year-old Asian male presented with fever, back pain, anorexia and weight loss. Physical examination revealed subcutaneous masses in the forehead, sternoclavicular joint, and right inguinal region. Computed tomography showed multiple osteosclerotic changes with soft structures and osteolytic changes. Both blood and sputum cultures were positive for Mycobacterium intracellulare, confirming the presence of disseminated NTM infection. Histopathological evaluation of the subcutaneous mass in the right inguinal region showed numerous granulomas consisting of epithelioid cells with Langhans-type giant cells. Anti-IFN-γ autoantibodies with suppression of IFN-γ-dependent signal transducer and activator of transcription 1 (STAT1) phosphorylation was detected. Interestingly, he was also diagnosed with idiopathic CD4 lymphocytopenia. Two-drug combination therapy with clarithromycin and ethambutol was started for the NTM infection, which resulted in a favorable disease course. Conclusions: In patients with disseminated NTM infection, anti-IFN-γ antibody positivity can be detected even in patients with idiopathic CD4 lymphocytopenia. Anti-IFN-γ neutralizing antibodies should be examined even in patients with idiopathic CD4 lymphocytopenia to elucidate the pathophysiology of disseminated NTM disease.