Felis ISSN 2398-2950

Scottish fold osteochondrodysplasia

Synonym(s): Chondrodysplasia

Contributor(s): David Godfrey, Prof Richard Malik

Introduction

  • Cause:
    • Scottish Fold cats have forward folded ears due to a cartilage abnormality. This breed-defining characteristic itself is benign but the intimately associated ostechondrodysplasia of the limbs can have devastating effects on cartilage and bone development elsewhere.
    • Cats homozygous for the abnormal gene develop severe osteoarthritis early in life. Such cats are no longer bred deliberately by breeders.
    • Heterozygous cats have less severe osteoarthritis. This can vary from a moderate to severe problem which develops in early adulthood, or a milder variant that only becomes problematic when cats are in late middle age to the geriatric years.
  • Signs
    • Foreshortened distal limbs (fore and hind), a short, inflexible tail.
    • Clinical signs of osteoarthritis, especially of distal joints, particularly the hocks.
    • Forward folding ears.
  • Diagnosis:
    • History and examination.
    • Imaging of limbs - radiology, scintigraphy (bone scan) and spiral CT.
  • Treatment:
    • There is no treatment for the genetic abnormality itself.
    • Osteoarthritis can be treated in the same ways as idiopathic osteoarthritis and osteoarthritis secondary to other causes with environmental modification, nonsteroidal anti-inflammatory drugs and nutraceuticals.
    • In severe cases, radiation therapy using either the radioisotope samarium or external beam from a LINAC can be used to kill pain fibers in the joints, which has a prolonged drug-free beneficial effect.
    • In the future autologous stem cell therapy may prove useful.
  • Prognosis:
    • Poor for severely affected individuals, although the disease can be palliated with acceptable quality of life in most individuals.
    • Guarded for less severely affected individuals as in the medium term progression is expected.
    • As this is a predictable genetic disease, it is strongly recommended that the breeding of these cats is not continued, for ethical and welfare considerations.

Pathogenesis

Etiology

  • Scottish Folds originated spontaneously in farm cats and the breed was developed by mating to British Shorthairs. After initially being recognized in the UK it was subsequently banned in the UK by the Governing Council of the Cat Fancy of Great Britain because of the associated common limb and tail deformities.
  • The distal limb bones defects are probably due to defective endochondral ossification with secondary degenerative joint disease occurring - synovitis and exostoses - due to the abnormal mechanical forces resulting from the deformities.
  • It's also possible that there is defective cartilage as a primary abnormality.
  • Recent molecular genetic investigations by Barbara Gandolphi, Bianca Haas and Leslie Lyons (plus various collaborators) have identified the underlying genetic defect, and a PCR test to identify affected animals.

Pathophysiology

  • Osteochondrodysplasia in Scottish folds is an autosomal dominant condition with high but incomplete penetrance.
  • Homozygous (Fd/Fd) individuals have severe disease.
  • Heterozygous Scottish fold cats with one mutated gene (Fd/fd) develop milder disease (there is some older literature that states these cats are unaffected but this appears to be incorrect, so long as individual cats are followed for a sufficiently long timeframe).
  • Homozygous (fd/fd) cats are called Scottish shorthairs or Scottish fold variants, they have normal-type ears and no associated osteoarthritis.

Timecourse

  • In homozygous cats lesions are evident on radiography from 7weeks of age.
  • In heterozygous cats lesions are evident on radiography from 6 months of age.
  • The disease is always progressive and incurable, and is thus life-long. Many cats will be euthanased early in life. However, advances in treatment of osteoarthritis with drugs such as pentosan   Pentosan polysulfate  , meloxicam, special diets and so forth have meant that most animals can be treated effectively enough to have reasonable quality of life. Severe cases benefit from radiation therapy, as stated earlier.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references fromVetMed Resource and PubMed.
  • Chang J, Jung J, Oh S, Lee S, Kim G, Kim H, Kweon O, Yoon J & Choi M (2007)Osteochondrodysplasia in three Scottish Fold cats.J Vet Sci8(3), 307-309PubMed.
  • Hubler M, Volkert M, Kaser-Hotz B, Arnold S (2004)Palliative irradiation of Scottish Fold osteochondrodysplasia.Vet Radiol Ultrasound45, 582-585PubMed.
  • Malik R, Allan G S, Howlett C R, Thompson D E, James G, McWhirter C, Kendall K (1999)Osteochondrodysplasia in Scottish Fold cats.Aust Vet J77,85-92PubMed.
  • Takanosu M, Takanosu T, Suzung H & Suzung K (2008)Incomplete dominant osteochondrodysplasia in heterozygous Scottish Fold cats.Journal of Small Animal Practice49, 197-199PubMed.

Other sources of information

  • Malik R (2001)Genetic diseases of cats.Proceedings of ESFM symposium at BSAVA Congress 2001, Birmingham, UK.


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