Disseminated Bacille Calmette-Guérin Vaccine-Induced Disease in a Sample of Iranian Children: A Longitudinal Case-Series Study

Background: Approximately a quarter-million Iranian newborns receive the Bacille Calmette-Gu & eacute;rin (BCG) vaccine annually.However, in immunodeficient infants, this vaccine can lead to disseminated BCG disease (DBD).Objectives: This study aims to determine the clinical presentation, comorbidities, underlying immunodeficiency, andprognosis of DBD in a group of Iranian children.Methods: In a longitudinal case-series study, data were collected from the files of infants and children diagnosed with DBDfrom 2005 to 2017. Immunodeficiency screening was conducted for each patient. For children with normal immunodeficiencyscreening results, further testing for Mendelian susceptibility to mycobacterial diseases (MSMD) was performed. Detection ofDBD in children was achieved by evaluating gastric lavage and bone marrow aspiration samples for mycobacterium.Results: Most of the 22 patients were immunocompromised, with the following distribution: 31.8% had severe combinedimmunodeficiency (SCID), 45.5% had MSMD (specifically IL-12R beta 1 deficiency), one patient (4.5%) had Wiskott-Aldrich syndrome(WAS), and the remaining 18.1% had unknown immunodeficiency types. Most patients with MSMD were successfully treated anddid not show relapse during the follow-up period, even after discontinuing anti-tuberculosis (TB) medications.Conclusions: Due to the similarity of its manifestations to sepsis, diagnosing systemic infections caused by the BCG vaccine inchildren requires a high level of clinical suspicion and appropriate diagnostic measures, such as mycobacterial culture,biochemical speciation, or polymerase chain reaction (PCR). These diagnostic steps should be taken promptly in cases of DBD,with concurrent treatment using anti-tuberculosis drugs and, if possible, targeted therapies for underlying immunodeficiency.