Anti-interferon-γ autoantibody-mediated immunodeficiency with disseminated Mycobacterium massiliense and secondary Sweet syndrome: A case report

RATIONALE: The co-occurrence of adult-onset immunodeficiency syndrome mediated by anti-interferon-γ autoantibodies (AIGA-AOID), disseminated non-tuberculous mycobacterial (NTM) infection, and Sweet syndrome is a recognized but underreported triad, particularly in East Asian populations. Detailed case reports emphasizing diagnostic approach and integrated management remain valuable for improving clinical recognition. PATIENT CONCERNS: A 70-year-old Asian female presented with a 1-year history of a progressive neck mass, a 6-month history of recurrent fever, and a painful cutaneous eruption on the face, trunk, and limbs. DIAGNOSES: Evaluations revealed disseminated Mycobacterium massiliense infection involving lymph nodes, lung, and skin. Skin biopsy was consistent with Sweet syndrome. High-titer anti-interferon-γ autoantibodies (1:2500) were detected, confirming AIGA-AOID in the absence of HIV or other immunosuppression. INTERVENTIONS: Combined therapy was initiated: rituximab (two weekly doses) with corticosteroids, and a 12-month oral antimycobacterial regimen (clarithromycin, moxifloxacin, linezolid). OUTCOMES: The patient showed marked clinical improvement within 2 weeks, with resolution of fever and skin healing. Follow-up imaging at 3 months demonstrated significant regression of lymphadenopathy and lung consolidation. LESSONS: Sweet syndrome can be a presenting sign of disseminated NTM disease. In immunocompetent-appearing adults, especially in endemic regions, this should prompt investigation for AIGA-mediated immunodeficiency. Early diagnosis and combined immunomodulatory-antimicrobial therapy are crucial for successful outcomes.