B cell–negative severe combined immunodeficiency (SCID) is caused by molecules involved in the variable (diversity) joining (V[D]J) recombination process. Four genes involved in the nonhomologous end joining pathway–Artemis, DNA-PKcs, DNA ligase 4, and Cernunnos–are involved in B cell–negative radiosensitive SCID. Deficiencies in DNA ligase 4 and the recently described Cernunnos gene result in microcephaly,
growth retardation, and typical bird-like facies. Lymphopenia and hypogammaglobulinemia with normal or elevated immunoglobulin (Ig) M levels indicate a defect in V(D)J recombination. We present a case with recurrent postnatal pulmonary infections leading to chronic lung disease, disseminated molluscum contagiosum, lymphopenia, low IgG, IgA and normal IgM levels. Our patient had phenotypic features
such as microcephaly and severe growth retardation. Clinical presentation in patients with the B cell–negative subtype ranges from SCID to atypical combined immunodeficiency, occasionally associated with autoimmune manifestations and cytomegalovirus infection. Our patient survived beyond infancy with combined immunodeficiency and no autoimmune manifestations.

Key words: Cernunnos. Immunodeficiency. Syndrome.