X-linked severe combined immunodeficiency disease (XSCID) is an immune disorder of basset hounds and Cardigan Welsh corgis. Affected pups have peripheral lymphopenia, with low or absent IgG and IgA, but normal IgM concentrations. Clinical findings include the absence of palpable lymph nodes, a small thymic shadow on radiographs, and chronic recurrent infections. It is invariably lethal. The breed specific mutations in IL2RG lead to production of a truncated protein.Affected pups are characterized by failure to thrive, absence of palpable peripheral lymph nodes, small thymic size, and T cells that are unresponsive to proliferative stimulation. Affected pups often succumb to chronic, recurrent, opportunistic infections in varied locations (ear, skin, intestine). Other signs include diarrhea, and intermittent vomiting. Vaccination of affected pups with modified live virus vaccines can induce viremia and clinical signs. Affected pups have peripheral lymphopenia with a normal percentage of B cells and a low to normal percentage of T cells. IgM concentrations are normal, but IgG and IgA concentrations are greatly reduced or absent (Pullen et al., 1997). Even with supportive treatment, affected pups usually die by 4 months of age. (From OMIA)