Incorrect diagnoses in patients with neutralizing anti-interferon-gamma-autoantibodies

Early diagnosis of adult-onset immunodeficiency associated with neutralizing anti-interferon-gamma autoantibodies (anti-IFNγ Abs) remains difficult given the lack of a distinctive phenotype and a routine test. This study aimed to investigate the determinants of incorrect tentative diagnoses and useful clues for early disease recognition. This study enrolled adult patients who had unexplained opportunistic infections diagnosed at six hospitals and identified those having neutralizing anti-IFNγ Abs (cases). Demographics, medical history, initial presentations and laboratory data, causative pathogens, tentative diagnoses, and treatment were analysed and compared among individuals having neutralizing anti-IFNγ Abs (cases) and those without (controls). Among the 154 patients enrolled, neutralizing anti-IFN-γ Abs were detected in 50 (71%) of 70 patients with disseminated non-tuberculous mycobacterial infection (dNTM) but not in 84 patients without dNTM. The median time from disease onset to the recognition of dNTM associated with neutralizing anti-IFNγ Abs was 1.6 years (range, 0.25–19 years). Incorrect tentative diagnoses resulted in the administration of anti-tuberculosis regimens (60%, 30/50), immunosuppressants (48%, 24/50), and systemic chemotherapy (2%, 10/50) to the 50 cases. Multivariate analysis revealed that case patients were more likely than controls to present with multiple bone lesions (adjusted odds ratio (OR), 27.16; 95% confidence interval (CI), 1.21–609.59) and leukocytosis (adjusted OR, 1.48; 95% CI, 1.12–1.95); however, the controls had a higher rate of mycobacterial bloodstream infection (adjusted OR, 0.05; 95% CI 0.00–0.66). The high rate of incorrect tentative diagnoses led to frequent inappropriate management in patients with neutralizing anti-IFNγ Abs, and highlighted the need for increased awareness among clinicians.