Genetic and clinical profiling of mendelian susceptibility to mycobacterial disease patients; single center experience

Objective: Mendelian susceptibility to mycobacterial disease (MSMD) is a subgroup of primary immunodeficiencies which develops with the Bacille Calmette–Guérin (BCG) vaccine or non-tuberculous mycobacterial infections. The clinical symptoms have a broad spectrum, from localized to disseminated infections. Materials and Methods: Herein, we performed whole-exome sequencing (WES) on 13 patients with MSMD phenotype. All variants were confirmed by Sanger sequencing. The mean age was 8.41 years (min 3 – max 14 years), and the mean age of symptom onset was 4.6 years in our cohort. Results: We found previously identified IFNGR1 (n=1), IFNGR2 (n=1), TYK2 (n=1), IL12RB1 (n=1), and CYBB (n=1) gene variants in nine patients. Our patients mostly suffered from lymphadenitis (61.5%), osteomyelitis (38%), and miliary tuberculosis (31%). All patients except one had had the BCG vaccination. Two patients developed BCGitis after vaccination. Three patients suffered from disseminated BCG infection (BCGosis). Conclusion: Our findings show the importance of molecular diagnosis in patients with severe infections as an approach for understanding the genetic basis of infectious diseases and deciding on treatment options. The deficiency of IFN-mediated immunity genes plays a crucial role in the pathogenesis of MSMD and must be considered in pediatric patients with BCGitis.