Severe combined immunodeficiency (terrier type) is an inherited disease affecting dogs. Affected dogs are unable to produce a protein important for proper immune function, predisposing them to severe recurrent or chronic bacterial, viral and fungal infections. Affected dogs often present with symptoms of disease around 12 to 14 weeks of age including failure to thrive, poor growth, weight loss, lethargy, diarrhea, vomiting and lack of palpable lymph nodes. Affected dogs may also present with active respiratory, skin, eye or ear infections. Puppies may die shortly after vaccination with modified live vaccines. Affected dogs die within 4 months of age.
Genetic testing of the PRKDC gene will reliably determine whether a dog is a genetic Carrier of severe combined immunodeficiency (terrier type). Severe combined immunodeficiency (terrier type) is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of being a carrier of the PRKDC gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
Bell TG, Butler KL, Sill HB, Stickle JE, Ramos-Vara JA, Dark MJ. Autosomal recessive severe combined immunodeficiency of Jack Russell terriers. J Vet Diagn Invest. 2002 May; 14(3):194-204.
Ding Q, Bramble L, Yuzbasiyan-Gurkan V, Bell T, Meek K. DNA-PKcs mutations in dogs and horses: allele frequency and association with neoplasia. Gene. 2002 Jan 23; 283(1-2):263-9.