Chondrodysplasia

• Literally means “abnormal cartilage development”
• Defective cartilage growth at the physis
• Usually genetic cause
• Occurs in cattle, dogs, sheep, pigs and cats
• Leads to disproportionate dwarfism (contrast with miniature breeds)
  • Generally, growth is disproportionate because only the growth of bones which form from cartilage models is retarded – growth of other bones is normal (i.e. long bones shorter than normal)

In Dogs:

• Localised forms occur in dogs (e.g. affecting skulls of Pekingese and Bulldogs or the limbs of Dachshunds and Bassett hounds)
• Occasionally seen in immature Beagles, Poodles, Alaskan Malamutes, Scottish Deerounds and Norwegian Elkhounds

In Cattle:

• Dexter cattle
  • Are heterozygous for incompletely dominant gene
  • When homozygous - lethal, producing 'bulldog calf'
    • A well recognised deformation in Dexter calves.
    • Related to defective cartilage matrix and abnormal ossification.
    • The calf is born with short and crooked limbs and the facial bones are short.
  • Usually aborted prior to seven month of pregnancy
  • Also occurs in Holstein, Jerseys and Charolais
  • Grossly:
    • Limbs and vertebral column are short
    • Domed cranium
    • Protruding tongue
    • Absent hard palate
    • Large umbilical hernia with eventrated abdominal organs
  • Histologically:
    • Proliferative and hypertrophic zones in the physes are irregularly separated by fibrovascular tissue
    • Chondrocytes are not properly arranged
    • Irregular ossification and mineralisation

• Telemark type
  • Cattle of Norwegian origin
  • Also seen in Jersey cows
  • Calves born alive, unable to stand and die soon after birth
  • Grossly:
    • Domed cranium
    • Brachygnatic face
    • Protruding tongue
    • Cleft palate
    • Short neck and limbs

• Brachycephalic 'Snorter' type
  • Hereford and Aberdeen Angus
  • Show nasal dyspnoea and chronic rumenal tympany
  • Grossly:
    • Short, broad head
    • Prominent, laterally displaced eyes
    • Short and compressed vertebral column
    • Distal long bones shorter than proximal
  • Histologically:
  • Physes appear normal
  • Pallisading chondrocytes fewer in number
  • Less hypertrophy

In Sheep:

• Ancon type
  • Short limbs due to premature closure of growth plates
  • Now rare
• Spider lamb
  • Hereditary (autosomal recessive) in Suffolk and Hampshire breeds in North America
  • Long, thin, angular limbs
  • May be born alive or dead, aborted or develop symptoms within a month of birth
  • Grossly:
    • Fine bones, poor musculature, small heads, scoliosis
  • Histologically:
    • Abnormal centres of endochondral ossification
    • Nodular cartilage hypertrophy

In Pigs:

• Occurs in Danish Landrace
• Autosomal recesive inheritance
• Dwarfs with short legs, forelegs shorter than hind legs
• Abnormal movement is noticable at weaning
• Sequel is arthrosis