X-Linked Severe Combined Immunodeficiency (IL2RG)
X-linked severe combined immunodeficiency is a pan-ethnic disorder caused by pathogenic variants in the gene IL2RG. It is inherited in an X-linked manner, and therefore typically only males are affected. Due to a lack of functional T cells, natural killer cells, and B lymphocytes, infants have severe and recurrent infections and exhibit a failure to thrive, rashes, diarrhea and frequent illnesses. Without a bone marrow transplant, the disease is fatal in infancy. Bone marrow transplant can be curative, but fatal complications can result. Some patients may have a milder form, known as atypical X-linked severe combined immunodeficiency. This form results in recurrent infections and reduced life expectancy. Alleles that retain some protein function, typically missense variants, are more likely to result in the atypical form, whereas null alleles are more likely to result in the severe form.
For information about carrier frequency and residual risk, please see the residual risk table.