Genetic susceptibility to Tuberculosis in an infant with BCG-osis

Abstract

Mendelian susceptibility to mycobacterial diseases (MSMD) is a group of innate immunity defects characterized by inborn susceptibility to intracellular pathogens. These are due to defects in the interleukin 12-23-interferon gamma y axis. Twenty-three genetic mutations have been identified in this axis, of which mutation in the IL12RB1 gene is the most common genetic defect of MSMD identified. An 11-month-old infant presented with features of axillary lymphadenitis and skin lesions both of which were positive for acid-fast bacilli on Ziehl– Neelsen stain and GeneXpert. Keeping a high index of suspicion of primary immunodeficiency, the child was evaluated further and was diagnosed as a case of MSMD with IL12RB1 gene mutation.