Generalized lymphadenopathy due to disseminated non-typhoidal Salmonella infection in a 3-year-old: Unmasking IL-12RB1-deficient MSMD - A rare case report.

IL-12 receptor β1 (IL-12Rβ1) deficiency is the most frequent genetic etiology of Mendelian Susceptibility to Mycobacterial Disease (MSMD), predisposing to severe infections with intracellular pathogens. We report a 3-year-old male with prior BCG adenitis and multidrug-resistant extra-pulmonary tuberculosis who presented with persistent generalized lymphadenopathy. Excisional lymph node biopsy grew Salmonella enterica serovar Typhimurium. Genetic testing revealed a homozygous pathogenic mutation in the IL12RB1 gene. This case illustrates a rare presentation of disseminated non-typhoidal salmonellosis in IL-12Rβ1 deficiency and highlights the importance of early immunological evaluation in children with recurrent, severe, or atypical infections.