Anti-interferon-γ Autoantibody-mediated Adult-onset Immunodeficiency with Disseminated Mycobacterium abscessus Complex Infection: A Report of Three Cases.

Interferon-γ serves as the pivotal cytokine for macrophage activation. Anti-interferon-γ autoantibody (AIGA)-mediated adult-onset immunodeficiency (AOID) represents a phenocopy of primary immunodeficiency, characterized by recurrent disseminated infections predominantly caused by Mycobacterium abscessus complex (MABC) and other nontuberculous mycobacteria. Disseminated MABC (dMABC) in AOID poses significant therapeutic challenges, requiring long-term multidrug antimicrobial therapy combined with AIGA-targeted immunotherapy. This report details three cases of AOID with dMABC. All patients exhibited recurrent fevers, widespread cutaneous erythema, nodules, pustules, and painful multifocal lymphadenopathy over several months to 2 years. Serum AIGA testing was positive in all cases. MABC was isolated from skin and lymph node specimens through culture or next-generation sequencing. Radiologic studies confirmed systemic involvement, including pulmonary, lymphatic, and osteoarticular sites. A therapeutic regimen of combined antibiotics and low-to-medium-dose oral glucocorticoids (prednisone 20-30 mg/day initiated, tapered to 5 mg/day maintenance) was instituted, leading to clinical resolution in all patients. All were discharged successfully and remained disease-free on long-term follow-up.