SCID is a disorder of the immune system
Severe combined immune deficiency
Breeds known to be affected
Arabian and related breeds
Foals affected by SCID lack a proper immune system which is critical for fighting infection. Once the maternal immune protection wears off, SCID foals develop signs of infection (examples including fever, respiratory distress and/or diarrhea). SCID cannot be cured and affected foals will usually die from an infection before 6 months of age.
SCID is a recessive disorder so two copies of the defective version of the DNA-PK gene must be inherited (SCID/SCID) for a foal to be affected. If a horse is a carrier (n/SCID), it will not show any clinical signs of SCID. However, there is a 50% chance it will pass the variant to its offspring, so mating to other carriers should be avoided to prevent the birth of an affected foal.
Interpretation of results
n/n: Horse does not carry the mutation associated with SCID.
n/SCID: Horse has one copy of the mutation associated with SCID.
SCID/SCID: Horse has two copies of the mutation associated with SCID.
Shin et al. A kinase-negative mutation of DNA-PK(CS) in equine SCID results in defective coding and signal joint formation. The Journal of Immunology 1997; 158:3565-3569.