Genetic disease of horse. 말의 유전병

A4. Most important genetic diseases of the horse ​

1. Haemophilia - x linked disease

- Lethal factors, gene mutations

- WW (white) & OO (ovaro white spotting)

- unable to produce blood clot —> u die , internal bleeding

- occure in welsh ponies

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​2. Fragile foal syndrome (warmblood)

- extensive lesions, ulceration and tearing of skin

- mutated LHI gene , need two copies .

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3. Lethal white ovaro (LWO) – Hirschsprung's disease

- TC  AG mutation in endothelin B receptor gene

- Linked with melanocyte migration regulator gene of neural crest

- Lack of colon ganglions -> no functional colon. The colon is affected

- AR (auto recessive) inheritance

- Signs: Colic & flatulence of suckling foals (gases) / Death of homozygotes

/ Seen in Paint, Pinto, Quarter horse, English thoroughbred, Miniature horse breeds

- Molecular diagnosis ​

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4. HYPP (hyperkalaemic periodic paralysis)

- Mis-sense point mutation, autosomal dominant

- Signs: Na channel function is disturbed in skeletal muscle, hyperkalaemia, lameness, muscle

weakness, paralysis, muscle twitching

- Occurs mainly in quarter horse, paint & appaloosa breeds

- Molecular genetic diagnosis (DNA test)​

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5. Severe combined immunodeficiency (SCID)

- Frameshift mutation, deletion in DNA-protein kinase genes, auto recessive inheritance

- Signs: Poor T & B-lymphocyte function, immunodeficiency, death of young foals (1-8 weeks) due to

2-degree infection after colostrum protection ceases

- Occurs in Arab horses (2-25% may be carriers)

- Molecular genetic diagnosis​

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6. Glycogen branching enzyme deficiency (GBED)

- No glycogen storage  cardiac & skeletal muscles cannot function  death

- Occurs in foals homozygous for lethal GBED allele

- DNA blood test​

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7. Melanomatosis of grey horses

- Disorder of melanocyte migration

- Signs: relatively benign melanomas in grey horses of 15yrs + around eyes, vagina, anus & on skin

- Occurs in most breeds of grey color

- Clinical diagnosis

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​8. Equine polysaccharide storage myopathy (EPSM/PSSM)

- Metabolic muscular condition  tying up

- Also related to glycogen storage disorder

- Seen in Quarter horses​

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9. Hereditary equine regional dermal asthenia (HERDA)

- Also known as hyperlastosis cutis (HC)

- Autosomal recessive

- Collagen defect  layers of skin are not held firmly together