Clinical Features, Genetic Background, and Outcomes in Chil-dren with Mendelian Susceptibility to Mycobacterial Disease Diagnosed with Mycobacterial Tuberculosis Complex in Saudi Arabia: Case Series

Background: While live attenuated BCG immunization is generally well tolerated by children, those with certain immunodeficiencies, including Mendelian susceptibility to mycobacterial disease (MSMD) are at high risk for potential adverse reactions. These can range from regional lymphadenitis to fatal disseminated BCG infection (BCGosis). Here, we describe the clinical features, investigations, and underlying primary diseases of MSMD patients in Saudi Arabia. Methods: This case series reports a retrospective descriptive analysis of patients under 14 years of age who were diagnosed with MSMD and developed disseminated BCGitis after vaccination, between January 2009 and December 2022. Results: Fourteen patients with disseminated BCG disease were enrolled. The most common symptom was fever, which presented in 9 (64%) of the patients, while GIT symptoms were documented in 5 (35%). The most common signs were localized lymphadenopathy, observed in 8 patients (57.1%), and hepatosplenomegaly in 6 patients (42%). All patients had evidence of Mycobacterium tuberculosis complex on culture and the majority were PCR-positive. They were all treated with anti-tuberculosis medications; in addition, 3 patients started rhIFN-γ therapy. There were 2 deaths among the 14 cases (14.3%). Conclusion: A thorough investigation for immunological defects is crucial in children who develop disseminated BCGitis, and early anti‐mycobacterial therapy is highly recommended in MSMD patients with BCG disease.