Difference between revisions of "Bones Developmental - Pathology"

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===Chondrodysplasia===
+
===[[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)
 
 
<u>In Dogs:</u>
 
*'''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
 
 
<u>In Cattle:</u>
 
*'''Dexter cattle'''
 
**Are heterozygous for incompletely dominant gene
 
**When homozygous - lethal, producing 'buldog calf'
 
**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 - Anatomy & Physiology|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 - Anatomy & Physiology|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
 
 
<u>In Sheep:</u>
 
*'''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 [[Bone & Cartilage Development - Anatomy & Physiology|endochondral ossification]]
 
***Nodular cartilage hypertrophy
 
 
<u>In Pigs:</u>
 
*Occurs in Danish Landrace
 
*Autosomal recesive inheritance
 
*Dwarfs with short legs, forelegs shorter than hind legs
 
*Abnormal movement is noticable at weaning
 
*Sequel is [[Joints Degenerative - Pathology#Degenerative joint disease (DJD)|arthrosis]]
 
 
 
[[Category:Bones - Developmental Pathology]]
 
  
  

Revision as of 17:59, 27 February 2011

Generalised

Dwarfism


Chondrodysplasia

Osteopetrosis (Marble bone disease)

  • Occurs in sheep, dogs, cattle, horses
  • Failure of resorption by osteoclasts -> failure of remodelling of cancellous bone
  • Bones become thickened and dense but brittle
  • Marrow cavites are full of unresorbed primary spongiosa
  • Thickened intramembranous bones of skull -> altered shape of brain
  • Associated with severe viral infections, e.g. FeLV, BVD
  • Hereditary in Angus cattle


Lysosomal storage disease

  • Excess accumulation of metabolites in lysosomes
  • Affects mainly nervous system
  • Also affects growth of cartilage


Osteogenesis Imperfecta

  • Cause of fragile bones in humans, very rarely in animals
  • Reported in Holstein and Charolais calves
  • Poor mineralisation of bones and teeth
  • Fractures are often present at birth


Congenital hyperostosis of pigs

Hyperostosis (Image sourced from Bristol Biomed Image Archive with permission)
  • Rare, genetic
  • Diaphysial dysplasia
  • Excessive periosteal intramembranous bone, particularly in long bones
  • Grossly:
    • Greatly thickened long bones
    • Tense, shiny skin, closely adherent to tissues below
  • Born dead or die soon after birth


Retention of elongated primary trabeculae

  • Happens due to impaired osteoclastic activity
  • Primary trabeculae do not transform into secondary and tertiary
  • Continue to elongate
  • Form a dense band beneath growth plate - growth retardation lattice
  • Dense spikules apparent on radiographs
  • Can be caused by distemper virus, bovine viral diarrhoea virus


Localised

  • Hemimelia - abscence of one of limb bones
  • Syndactylia - fusion of toes
  • Polydactylia - increased number of digits
  • Ectrodactylia - cleft in paw extending to metacarpus of dogs and cats


Cervical Vertebral Stenotic Myelopathy (Wobblers)

  • Equine disease
  • Narrowing of the vertebral canal due to malalignment or maldevelopment of the vertebrae
  • Fast growing male TBs ranging from 8 months to 4 years
  • Hind limb ataxia due to cord compression


Angular limb deformity

  • Lateral deviation of distal portion of limb (valgus)
  • Medial deviation of distal portion of limb (varus) - more rare
  • Most common in foals
    • Carpal joint
    • Tarsal joint
    • Fetlock joint
  • Congenital or acquired
  • Due to:
    • Malpositioning in utero
    • Excessive joint laxity
    • Hypothyroidism
    • Trauma
    • Overnutrition
    • Defective endochondral ossification
    • Poor conformation
    • Disruption of blood supply to one side of bone
    • Secondary to physitis in horses
  • Usually resolves spontaneously in one to two weeks of life
  • More severe cases exceding compensatory capabilities will persisist
  • Cartilage development is affected


Fibrous dysplasia


Physitis

  • In horses
  • Often associated with angular limb deformity
  • Also called epiphysitis and physeal dysplasia
  • Problem of endochondral ossification
  • Two age groups
    • Weanlings
    • Yearlings in early training and two-year-olds
  • May cause contracted tendons and flexural deformities
  • Factors probably involved in its development:
    • Genetically fast growth rate
    • Large quantities of imbalanced, high energy feed
    • Imbalanced weight-bearing on joints
    • Excessive activity
    • Growth spurts
  • Histologically: (appearance similar to angular limb deformity)
    • Lateral aspect of radius
      • Thickened metaphyseal part of physeal cartilage
      • -> Delay or disturbance of endochondral ossification
      • Compression
    • Central part
      • No obvious deformity
    • Medial aspect
    • Laxity of periarticular attachements in young foals allows angular limb deformity; not occuring in older foals and young horses
    • (Sustained trauma produces similar lesions)



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Developmental abnormalities