Severe immunodeficiency spectrum associated with NHEJ1 gene mutation: Cernunnos/XLF deficiency.

Cernunnos/XLF deficiency is a rare, severe combined immunodeficiency, inherited in an autosomal recessive pattern (OMIM number: 611290), related to the NHEJ1 gene. This gene participates in the DNA non-homologous end-joining pathway, repairing double-strand breaks in the DNA of mammalian cells. The clinical features include growth retardation, microcephaly, triangle-shaped face, recurrent infections, fibroblast's excessive sensitivity to gamma-ionizing radiation, and hypogammaglobulinemia; also, low counts of subpopulations of B and T lymphocytes, with normal values of natural-killer cells. This manuscript aims to present an extremely rare case of combined immunodeficiency in a twenty-years-old man with non-consanguineous parents and a homozygote variant of the NHEJ1 gene. This case is the fiftieth reported in the literature and the first in Colombia, given the low prevalence of NHEJ1-related immunodeficiency and its difficult diagnosis due to scarce knowledge.