Severe combined immunodeficiency disease (SCID) of horses is an autoso
mal, recessive hereditary disease occurring among Arabian horses. The
genetic defect responsible for this disease was recently identified as
a 5-basepair deletion in the gene encoding DNA-protein kinase catalyt
ic subunit (DNA-PKcs). Horses with one copy of the gene appear normal,
while horses with two copies of the gene manifest the disease. The pr
esent report describes a PCR-based test for detection of the gene defe
ct and the results from testing 250 randomly selected Arabian horses.
The frequency of SCID gene carriers was 8.4% (21/ 250). Based on the g
ene frequency reported here, the authors would expect 0.18% (1 out of
567) of Arabian foals to be affected with SCID based on a random breed
ing population.