Cervical Mycobacterium genavense infection in a patient with lymphadenitis and previously unknown anti-IFN-γ IgG autoantibodies

BACKGROUND: Infections with atypical mycobacteria are rare and sometimes difficult to correctly diagnose. In many cases underlying diseases such immune deficiency can promote these infections. CASE PRESENTATION: A 43-year-old male of Southeast Asian origin presented to our tertiary care hospital with persistent cervical lymphadenopathy non-responsive to antibiotics. Imaging suggested malignancy, but a biopsy did not confirm this suspicion. PCR diagnostics identified Mycobacterium genavense and further immunological testing revealed an acquired adult-onset immunodeficiency due to neutralizing anti-IFN-γ autoantibodies (nAIGA), explaining both the current infection and previous pleural empyema. The patient responded well to triple antimycobacterial therapy, with no recurrence or novel infection after almost two years. CONCLUSIONS: Our case highlights the importance of considering underlying immunodeficiencies and the patient's geographic origin in the diagnosis of rare infections.