X-linked severe combined immunodeficiency disease (SCID) is caused by mutations in the interleukin (IL)-2 receptor γ (IL2RG) gene and patients usually present with a TBNK SCID phenotype.
The cytokine interleukin-21 (IL-21) is closely related to IL-2 and IL-15, and their receptors all share the common cytokine receptor gamma chain, gammac, which is mutated in humans with X-linked severe combined immunodeficiency disease (XSCID).
X-linked severe combined immunodeficiency disease (SCID) results from mutations of IL2RG, the gene encoding the interleukin-2 receptor gamma chain, also known as the common gamma chain (gamma c).