Cernunnos deficiency associated with BCG adenitis and autoimmunity: First case from the national Iranian registry and review of the literature

•A severe combined immunodeficiency (SCID) patient with T- B + phenotype who had a mutation in Cernunnos gene•The patient was associated with BCG adenitis and autoimmunity that less is observed in patients with Cernunnos deficiency•Our patient had BCG adenitis and autoimmunity•Normal B-cell, IgA and IgM suggesting a leaky form of the Cernunnos deficiency

Non-homologous end-joining (NHEJ) is a pathway that repairs double-strand breaks (DSB) in DNA and plays a vital role in V(D)J recombination of immunoglobulin genes. Cernunnos is a DNA repair factor that is involved in nonhomologous end-joining (NHEJ) process. Impairment in Cernunnos leads to a genetic disease characterized by neural disorders, immunodeficiency and increased radiosensitivity. We herein describe a severe combined immunodeficiency (SCID) patient with T- B + phenotype who had a mutation in Cernunnos gene and manifested recurrent infections, microcephaly and growth retardation with hypogammaglobulinemia. Furthermore, our patient was associated with BCG adenitis and autoimmunity that less is observed in patients with Cernunnos deficiency. In contrast to previous reported Cernunnos-deficient patients, our patient had normal B-cell number along with normal IgA and IgM, suggesting a leaky form of the Cernunnos deficiency due to residual count of B cells in our patient. Cernunnos deficiency should be considered in children with recurrent bacterial infections, microcephaly and growth retardation, in spite of having normal B-cell as well as normal IgM and IgA level.