Welcome to the Corgi Corner! We started a series that is posted on the first Saturday of every month! These posts will help spread education and awareness on topics like general dog care, corgi specific things, medical care, health facts, etc. This month’s Corgi Corner post will be all about X-linked severe combined immunodeficiency disease! X-linked severe combined immunodeficiency disease (X-SCID) is a rare and fatal genetic disorder that severely compromises the immune system. X-SCID dogs cannot produce functional B-lymphocytes and T-lymphocytes. B-lymphocytes are the cells responsible for producing antibodies and long-term “memory” of infection. T-lymphocytes can act to destroy infected cells as well as direct other immune cells to do their jobs. In the absence of a functional immune system, the dog is extremely susceptible to infections. X-SCID is caused by a mutation in the IL2RG gene, which provides instructions for a protein called the “common gamma chain”. X-SCID puppies appear normal at birth because they are protected by their mother’s antibodies. As this maternal immunity wanes around 6-8 weeks of age, symptoms appear as the puppy’s own immune system fails to function. So most X-SCID dogs are identified as puppies shortly after weaning or when initially vaccinated with modified live products. Genetic and laboratory testing, along with clinical signs, are used to diagnose X-SCID. A veterinarian may suspect X-SCID based on recurring, untreatable infections and a lack of palpable lymph nodes. Bloodwork reveals a severely reduced number of T-lymphocytes, though B-lymphocytes may be present in normal numbers. Antibody levels are often abnormal. A definitive diagnosis can be made through genetic testing, which identifies the specific mutation in the IL2RG gene. Due to the fatal nature of the disease, diagnosis is often confirmed post-mortem, revealing a severely underdeveloped thymus. There is currently no cure for X-SCID in dogs, and the prognosis is extremely poor. Supportive care, such as treating secondary infections with antibiotics, is the only option. However, the response to treatment is typically poor. Due to the debilitating and fatal nature of the disease, humane euthanasia is often recommended to prevent suffering. Experimental treatments like bone marrow transplantation and gene therapy have been used in research settings to study the disease and potentially correct the immune deficiency. However, these treatments are not widely available for clinical use. X-SCID has only been identified in Cardigan Welsh Corgis and Basset Hounds. It has a sex-linked recessive inheritance pattern, which means that the gene is on the X-chromosome. This means females must have two copies of the variant to be at risk of developing this condition, whereas male dogs only need one copy to be at risk. This means that males generally have a more poor prognosis compared to females. Since affected puppies do not live very long, the gene is generally passed down from the mother, who is a carrier with only one copy of the gene. So it is 100% preventable with genetic testing and reputable breeding practices. Reputable breeders will test their dogs prior to breeding to determine how many copies of the X-SCID gene they carry. They will also provide proof of this to any potential new puppy parents.