Severe combined immunodeficiency disease, SCID

 

Gene: PRKDC

Transmission: Autosomal recessive

For an autosomal recessive genetic disease an animal must have two copies of the mutation in question to be at risk of developing the disease.  Both parents of an affected animal must be carriers of at least one copy of the mutation.  Animals that have only one copy of the mutation are not at risk of developing the disease but are carrier animals that can pass the mutation on to future generations.

Mutation: Deletion PRKDC gene; c.9478_9482 del.5bp, p.(N3160 fs STOP 3,) exon70

Medical systems: Immunological, blood

Breeds: Arabian Horse, Arabian Horse Hybrids

Age of onset of symptoms: From birth or a few months after birth

Severe combined immunodeficiency disease (SCID) is a genetic disorder that occurs in 0.2% of Arabian Horses or Arabian Horse crosses.  The disease is characterized by significant immune deficiency where affected individuals are unable to produce immune responses against antigens such as bacteria and viruses.  Affected foals show symptoms including bacterial infections, acute diarrhea, listlessness, stunting and pneumonia.  SCID is fatal in doubly mutated (M/M, homozygous mutated) foals, who will not survive more than four to six months and often die from an opportunistic infection.  Heterozygous carriers (M/N) are often asymptomatic, but may have a higher incidence of neoplasia such as virus-induced sarcoidosis.

 

References:

OMIA link: [0220-9796]

Ayad A, Almarzook S, Besseboua O, et al. (2021) Investigation of cerebellar abiotrophy (CA), Lavender Foal Syndrome (LFS), and severe combined immunodeficiency (SCID) variants in a cohort of three MENA region horse breeds. Genes (Basel) 12:1893. [pubmed/34946842]

Bugno-Poniewierska M, Stefaniuk-Szmukier M, Piestrzyńska-Kajtoch AP, et al. (2019) Genetic screening for cerebellar abiotrophy, severe combined immunodeficiency and lavender foal syndrome in Arabian horses in Poland. Vet J 248:71-73.  [pubmed/31113566]

Crisman MV, Scarratt WK. (2008) Immunodeficiency disorders in horses.  Vet Clin North Am Equine Pract. 24(2):299-310. [pubmed/18652957]

Ding Q, Bramble L, Yuzbasiyan-Gurkan V, et al. (2002) DNA-PKcs mutations in dogs and horses: allele frequency and association with neoplasia. Gene. 283(1-2):263-9. [pubmed/11867233]

Shin EK, Perryman LE et Meek K. (1997) A kinase-negative mutation of DNA-PK(CS) in equine SCID results in defective coding and signal joint formation. J Immunol. 158(8):3565-3569. [pubmed/9103416]