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X-Linked Severe Combined Immunodeficiency (IL2RG gene, Basset Hound)

X-Linked Severe Combined Immunodeficiency (IL2RG gene, Basset Hound)

Severe combined immunodeficiency or X-linked SCID is a rare genetic disease characterized by a dysfunctional or absent immune system and alterations in lymph node development that may be absent.

Symptoms

There is a deficit in the production of T and B lymphocytes, the immune cells that fight infection and disease. This means that affected puppies are highly susceptible to infections, even those that would not normally be problematic for a dog with a healthy immune system. The first symptoms can appear from birth and are severe.

Disease Management

There is currently no cure for X-linked SCID. Given the severity of the symptoms puppies usually do not survive beyond 4 months.

Genetic basis

This disease follows an X-linked recessive mode of inheritance. Recessive X-linked inheritance means that female dogs must receive two copies of the mutation or pathogenic variant (one from each parent) to develop the disease, whereas males need only one copy of the mutated gene or variant from the dam to develop the disease. Male dogs usually show symptoms of the disease. Each male puppy born to a mother carrying the mutation has a 50% chance of inheriting the mutation and thus the risk of developing the disease. Bitches that do not carry the mutation are not at increased risk of having affected puppies. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

X-linked severe combined immunodeficiency is a failure of cellular and humoral immune responses caused by mutations in the IL2RG gene, resulting in the absence of T cells and dysfunctional B lymphocytes. As in humans, this disease in dogs causes affected animals to have serious immunity problems and die within a few weeks of life. The IL2RG gene encodes for the gamma subunit of the interleukin-2 receptor, which is an essential molecule for the proper functioning of the immune system. The gamma subunit interacts with molecules known as cytokines that promote lymphocyte proliferation, differentiation, survival and function. Henthorn et al. identified the c.30_33del mutation of the IL2RG gene as the cause of immunodeficiency in basset hounds.

Most affected breeds

Basset Hound

Bibliography

Henthorn PS, Somberg RL, Fimiani VM,et al. IL-2R gamma gene microdeletion demonstrates that canine X-linked severe combined immunodeficiency is a homologue of the human disease. Genomics. 1994 Sep 1;23(1):69-74.