A genetic diagnosis was established in 88%. ResultsĪmong 1.9 million screened newborns, 88 patients with congenital T-cell lymphocytopenia were identified (25 SCID, 17 leaky SCID/Omenn syndrome (OS)/idiopathic T-cell lymphocytopenia, and 46 syndromic disorders). The Working Group for Pediatric Immunology (API) and German Society for Newborn Screening (DGNS) performed 6-monthly surveys to assess the TREC-NBS process after 2.5 years. MethodsĬhildren with abnormal TREC-NBS were referred to a newly established network of Combined Immunodeficiency (CID) Clinics and Centers. *This article may not be reproduced without the written consent of the UC Davis Center for Equine Health.T-cell receptor excision circle (TREC)-based newborn screening (NBS) for severe combined immunodeficiencies (SCID) was introduced in Germany in August 2019. UC Davis Veterinary Genetics Laboratory - Arabian/Arabian Cross Horse Genetic Tests The owners of a mare that produces an affected foal are required to notify the stallion owner immediately. The Arabian Horse Association (AHA) Code of Ethics requires disclosure of known carrier status of SCID, if known, for “any horse capable of reproducing that is being offered for breeding, sale, or lease”. Matings between two SCID carriers have a 25% chance of producing SCID foals, and are not recommended. Results can be used to identify carriers and to select appropriate mating pairs. The test is recommended for horses from lineages that have produced SCID foals. How can severe combined immunodeficiency be prevented?īreeders and owners can utilize the available DNA test to avoid producing SCID-affected foals. The prognosis for SCID is grave, and most foals die from infections by 5 months of age. What is the prognosis for severe combined immunodeficiency? Supportive therapy to address infections can be attempted, but medical management of SCID foals is ultimately unsuccessful. How is severe combined immunodeficiency treated? The available genetic test can be used to make a definitive diagnosis. Severe combined immunodeficiency must be distinguished from other conditions such as failure of passive transfer or selective IgM deficiency for an accurate diagnosis. Persistently low lymphocyte counts (lymphopenia) and low immunoglobulin (IgM) are common in SCID-affected foals, and may be indicators of the disease. How is severe combined immunodeficiency diagnosed? Depending on the type of infection, other signs can include diarrhea, lameness, colic, impaired growth, and weight loss. Common clinical signs include those associated with respiratory tract infections such as coughing, nasal discharge, and increased respiratory sounds. As protective antibodies from mare’s colostrum wane, foals become more susceptible to infections, with the first clinical signs of SCID often appearing around 2-3 months of age. What are the clinical signs of severe combined immunodeficiency?Īffected foals are normal at birth. There is no cure for SCID and affected foals die or are euthanized within the first six months of life. As a result, SCID foals are highly susceptible to viral, bacterial, fungal and protozoal infections from which they cannot recover. A DNA test is available.Īffected foals do not produce functional B and T lymphocytes, and in turn cannot mount appropriate immune responses to challenges. A mutation in the DNA-dependent protein kinase ( DNA-PK) gene, which codes for an enzyme critical to the development of the immune system and the ability to protect against infections, has been identified in affected individuals. Inherited as an autosomal recessive disorder, SCID has been identified in horses of Arabian and part-Arabian descent. Severe combined immunodeficiency (SCID) is a disease that causes foals to be born with severely weakened immune systems. What is severe combined immunodeficiency? A causative mutation has been identified and a genetic test for SCID is available.There is no cure for SCID and affected foals typically do not survive past six months of age.Affected foals are highly susceptible to infections from which they cannot recover.SCID is an autosomal recessive inherited condition identified in Arabian and part-Arabian horses.Foals with severe combined immunodeficiency (SCID) are born with severely weakened immune systems.
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