Scottish fold osteodystrophy

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Radiographs of a Scottish Fold showing shortened dysplastic metatarsal bones due to chondrodystrophy[2]

Scottish fold osteodystrophy is a genetic disease characterized by skeletal deformations of the vertebrae, metacarpal and metatarsal bones, and phalanges[3].

The Scottish Fold is one of the rarest purebred cats in Australia. One of the features of this breed of cats is the forward-folding ears which develops from 2 - 4 weeks of age, which is a physical feature that made the breed so attractive, but which comes as an incomplete dominant disease associated with abnormal and sometimes crippling endochondral ossification. Kittens with radiologically evident bone lesions are only produced from fold-to-fold matings[4].

As a result of these findings, the breed was banned in England in the mid 1970s, but was eventually exported to the USA where they were outcrossed with other breeds to produce the Scottish shorthairs (Scottish Fold straight ears or Scottish Fold variant)[5]. The Scottish shorthair developed a number of skeletal abnormalities such as an abnormal, inflexible tail base, shortened feet, abnormal gait and consequent lameness[6].

Clinical symptoms may present from weaning onwards, with symptoms of arthritis worsening as the kitten grows to maturity. Affected homozygous cats (fold-to-fold matings) are lame, and affected bones are deformed and swollen. All Scottish Fold-related cats with folded-ear phenotype, even if heterozygotes, suffer from some degree of osteochondrodysplasia of the distal limbs[7].

A partial, left-sided conduction deafness has also been reported associated with this disease[8].

Radiographic changes mainly include exostosis and secondary arthritis around affected joint lesions, and defective conformation in the phalanges and caudal vertebrae. The oral chondroprotective agents such as glucosamine and chondroitin sulfate have improve clinical well-being of feline patients but surgical intervention is usually required to improve mobility in most affected cases. Radiation therapy has also been attempted in some cats, with clinical improvement reported[9].

Since the prognosis of clinically affected cats with bone abnormalities is guarded to poor in most cases, it is suggested that breeding of fold-eared cats should be severely limited, and if used at all, they should be mated only to normal-eared cats[10].

References

  1. Scottish Fold of Calgary
  2. Chang J et al (2007) Osteochondrodysplasia in three Scottish Fold cats. J Vet Sci 8(3):307-309
  3. Gunn-Moore DA et al (1996) Unusual metaphyseal disturbance in two kittens. J Small Anim Pract 37(12):583-590
  4. Jackson OF (1975) Congenital bone lesions in cats with folded ears. Bull Fel Advis Bur 14:2-4
  5. Robinson R & Pedersen NC (1991) Normal genetics, genetic disorders, developmental anomalies and breeding programmes. In: Pratt, editor. Feline husbandry diseases and management in the multicat environment. American Veterinary Publications, Goleta. pp:75-76
  6. Wastlhuber J (1991) History of domestic cats and cat breeds. In: Pratt, editor. Feline husbandry diseases and management in the multi-cat environment. American Veterinary Publications, Goleta. pp:12-14
  7. Takanosu M et al (2008) Incomplete dominant osteochondrodysplasia in heterozygous Scottish Fold cats. J Small Anim Pract 49(4):197-199
  8. Mathews KG et al (1995) Resolution of lameness associated with Scottish fold osteodystrophy following bilateral ostectomies and pantarsal arthrodeses: a case report. J Am Anim Hosp Assoc 31(4):280-288
  9. Hubler M et al (2004) Palliative irradiation of Scottish Fold osteochondrodysplasia. Vet Radiol Ultrasound 45(6):582-585
  10. Malik R et al (1999) Osteochondrodysplasia in Scottish Fold cats. Aust Vet J 77(2):85-92