Background and objective. The Bacillus Calmette-Guérin (BCG) vaccine may cause severe complications in children with inborn errors of immunity (IEI), particularly in those with severe combined immunodeficiency (SCID), Mendelian susceptibility to mycobacterial disease (MSMD), and chronic granulomatous disease (CGD). This study aimed to describe the clinical spectrum, immunological characteristics, and outcomes of BCG-related complications in pediatric patients with IEI. Methods. We conducted a retrospective, single-center descriptive study including children with confirmed IEI who developed BCG-related complications and were followed at the Ibn Rochd Children’s Hospital, Casablanca, between 2004 and 2023. HIV-infected patients were excluded. Clinical presentation, immunological findings, genetic analyses, and outcomes were reviewed. Results. Forty-eight children were included, with a mean age of 10.8 months and a male predominance (58.3%). The cohort comprised three main groups according to the underlying immunodeficiency: severe combined immunodeficiency (SCID, n = 20), Mendelian susceptibility to mycobacterial disease (MSMD, n = 14), and chronic granulomatous disease (CGD, n = 9). Five additional patients with atypical lymphocytic phenotypes were analyzed separately. Consanguinity was reported in 45% of cases. BCG-related complications were classified as localized in 25% of patients, locoregional in 44%, and disseminated in 31%. Clinical manifestations included lymphadenitis, bone and skin involvement, and systemic symptoms. Genetic confirmation was available for all patients with MSMD and for a subset of patients with SCID and CGD. Disseminated forms were more frequent among children with SCID. Conclusion. BCG-related complications may represent an important early manifestation of underlying IEI in infancy, particularly in severe forms such as SCID. These findings highlight the need for increased clinical awareness of IEI in infants presenting with post-BCG complications.
