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| − | ===Chondrodysplasia=== | + | ===[[Chondrodysplasia]]=== |
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| − | *Literally means “abnormal cartilage development”
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| − | *Defective cartilage growth at the physis
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| − | *Usually genetic cause
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| − | *Occurs in cattle, dogs, sheep, pigs and cats
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| − | *Leads to '''disproportionate dwarfism''' (contrast with miniature breeds)
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| − | **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)
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| − | <u>In Dogs:</u>
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| − | *'''Localised''' forms occur in dogs (e.g. affecting skulls of Pekingese and Bulldogs or the limbs of Dachshunds and Bassett hounds)
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| − | *Occasionally seen in immature Beagles, Poodles, Alaskan Malamutes, Scottish Deerounds and Norwegian Elkhounds
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| − | <u>In Cattle:</u>
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| − | *'''Dexter cattle'''
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| − | **Are heterozygous for incompletely dominant gene
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| − | **When homozygous - lethal, producing 'buldog calf'
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| − | **Usually aborted prior to seven month of pregnancy
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| − | **Also occurs in Holstein, Jerseys and Charolais
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| − | **Grossly:
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| − | ***Limbs and vertebral column are short
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| − | ***Domed cranium
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| − | ***Protruding [[Tongue - Anatomy & Physiology|tongue]]
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| − | ***Absent hard palate
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| − | ***Large umbilical hernia with eventrated abdominal organs
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| − | **Histologically:
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| − | ***Proliferative and hypertrophic zones in the physes are irregularly separated by fibrovascular tissue
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| − | ***Chondrocytes are not properly arranged
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| − | ***Irregular ossification and mineralisation
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| − | *'''Telemark type'''
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| − | **Cattle of Norwegian origin
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| − | **Also seen in Jersey cows
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| − | **Calves born alive, unable to stand and die soon after birth
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| − | **Grossly:
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| − | ***Domed cranium
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| − | ***Brachygnatic face
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| − | ***Protruding [[Tongue - Anatomy & Physiology|tongue]]
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| − | ***Cleft palate
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| − | ***Short neck and limbs
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| − | *'''Brachycephalic 'Snorter' type'''
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| − | **Hereford and Aberdeen Angus
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| − | **Show nasal dyspnoea and chronic rumenal tympany
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| − | **Grossly:
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| − | ***Short, broad head
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| − | ***Prominent, laterally displaced eyes
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| − | ***Short and compressed vertebral column
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| − | ***Distal long bones shorter than proximal
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| − | **Histologically:
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| − | **Physes appear normal
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| − | **Pallisading chondrocytes fewer in number
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| − | **Less hypertrophy
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| − | <u>In Sheep:</u>
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| − | *'''Ancon type'''
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| − | **Short limbs due to premature closure of growth plates
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| − | **Now rare
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| − | *'''Spider lamb'''
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| − | **Hereditary (autosomal recessive) in Suffolk and Hampshire breeds in North America
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| − | **Long, thin, angular limbs
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| − | **May be born alive or dead, aborted or develop symptoms within a month of birth
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| − | **Grossly:
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| − | ***Fine bones, poor musculature, small heads, scoliosis
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| − | **Histologically:
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| − | ***Abnormal centres of [[Bone & Cartilage Development - Anatomy & Physiology|endochondral ossification]]
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| − | ***Nodular cartilage hypertrophy
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| − | <u>In Pigs:</u>
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| − | *Occurs in Danish Landrace
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| − | *Autosomal recesive inheritance
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| − | *Dwarfs with short legs, forelegs shorter than hind legs
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| − | *Abnormal movement is noticable at weaning
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| − | *Sequel is [[Joints Degenerative - Pathology#Degenerative joint disease (DJD)|arthrosis]]
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| − | [[Category:Bones - Developmental Pathology]]
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