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54 Cards in this Set

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Skeletal dysplasia
Abnormal development of bone
Skeletal dysplasia
- 2 types
Generalised dysplasia

Localised dysplasia
Generalised dysplasias (5 types)
chondrodysplasia
osteogenesis imperfecta
osteopetrosis
hyperostosis
osteochondromatosis
Ch______
Osteo___ ____
Osteo____
Hyper____
Osteochondro_____
Chrondrodysplasia
- definition
- bones most affected
- aka
Underlying defect in cartilage formation

Affects bones formed by endochondrial ossification (long bones, vertebra, basocranial)

Disporportionate dwarfism
Examples of chondrodysplasia in cattle
Examples of chondrodysplasia in sheep
Note: spider lamb exception with long limbs
Examples of chondrodysplasia in dogs
Inherited defect in Alaskan Malamutes, English pointer, Scottish Deerhound & others
Why do the tongues stick out in chrondrodysplastic animals?
Soft tissue growth is not affected
Features of long bones in most chondrodysplasias
Epiphyses are enlarged and mushroom shaped dt
arrested interstitial growth along with normal appositional growth
Varus
Valgus
Valgus is knock-kneed
Osteodysplasia
Abnormal development of bone
Osteogenesis imperfecta
- cause
- pathogenesis
Inherited defect in Type I collagen
Autosomal dominant in some breeds

Abnormal bone shape
Susceptibility to fractures
Osteogenesis imperfecta

Cattle breed most affected
Osteopetrosis
- cause
- pathogenesis
Defective osteoclast function

Poor remodelling, increased fragility

mostly a LETHAL trait
Osteopetrosis
- unusual features of long bones
Osteoclast defect - Medullary cavity filled with coarsely woven bone and cartilage - Thin diaphyseal cortices
Congenital hyperostosis
- affects
- pathogenesis
Inherited disorder in Landrace pigs

Thick limbs dt

subperiosteal fibrosis and new bone deposition

possibly due to vascular drainage anomaly
Exostosis
Benign new growth projecting from bone surface and characteristically capped by cartilage
Osteochondromatosis
Inherited condition in humans, dogs & horses

Single or multiple tumour-like exostoses
3 main generalised dysplasia
- brief cause
Chondrodysplasia: defect in cartilage formation

Osteogenesis imperfecta: defect in Type I collagen

Osteopetrosis: defect in osteoclast function
Localised skeletal dysplasia
- 4 main sites
Limbs
Skull
Vertebrae
Cervical vertebrae
What's this?
Syndactylyl
Polydactyly
What's this?
What's the opposite called?
Brachygnathia inferior
opp = brachygnathia superior
Scoliosis

Kyphosis
Scoliosis: lateral deviation of the spine

Kyphosis: dorsal deviation of the spine (humpbacked)
Spina bifida
- most common in which animal
Defective closure of dorsal vertebral laminae in a segment of the vertebral column (dt defective neural tube closure)

Manx cats (lethal)
"Wobbler syndrome"

- correct name
Cervical vertebral stenotic myelopathy
Cevical vertebral s____ m_____
"Wobbler syndrome"
- animals most affected
Horses & large breed dogs (esp Great Danes, Dobermans)
"Wobbler syndrome"
- 2 forms
Cervical vertebral instability
- cord damage is due to abnormal movement of neighbouring vertebra

Cervical static stenosis
- static lesion, present in all neck postures
"Wobbler syndrome"
- pathogenesis in horses
Cervical instability most common

- high energy diets fed to genetically predisposed yearlings

- C3 - C5 often

- progressive hind limb ataxia dt compression or stretching of cord
Transection of cervical spinal cord from horse
Wobbler Syndrome

Cervical vertebral stenotic myelopathy

"cervical vertebral instability" form
2 genetic diseases INdirectly affecting the skeleton
Lysosomal storage diseases
- mucopolysaccharidoses
- GMI gangliosidosis

Congenital erythropoietic porphyria
Genetic diseases INdirectly affecting the skeleton

- Systems most affected
CNS principally affected

Also skeletal deformities
Samples from cattle
What condition is this showing?
Congenital erythropoietic porphyria
Congenital erythropoietic porphyria
- pathogenesis in cattle
Inherited enzyme deficiency leading to accumulation of porphyrins in blood, bone, other tissues

Red brown discolouration of teeth and bones
Teeth & bones -> cherry red with UV exposure

Mild-mod anaemia
Photosensitisation if deposited in skin
What are "acorn calves"?

What is the likely cause?
Acorn calves have skeletal abnormalities
- disporportionate dwarfism, joint laxity
- sometimes vargus, valgus
- sometimes brachygnathia superior

Possible dt in utero exposure to a MYCOTOXIN (acorns are blameless!)
What's this?
Valgus (knock knees) Varus (bow legs)
Viruses affecting bone cell activity
BVDV (a pestivirus)
Classical swine fever (a pestivirus)
Canine distemper virus
FeHV

- possible dt viral destruction of osteoclasts (same cell lineage as monocytes/macrophages)
What's the arrow pointing to?
"Growth arrest lattices"
dt impaired remodelling due to reduced osteoclast activity
What's the difference between "growth arrest lattices" and "growth arrest lines"
Growth arrest lattices are primary trabeculae that do not remodel dt paucity of osteoclasts - may resolve once antigen removed (eg canine distemper)

Growth arrest lines are due to reduced bone growth often dt malnutrition or starvation. It is a horizontal plate of bone, signaling interrupted growth.
What's this showing?
Malnutrition or starvation retard longitudinal bone growth, thin the physis and form a bony plate in the metaphysis.

Resumption of growth following correction forms a growth arrest line (radiotranslucent)
What's this?
What's it due to?
Cyclops lamb
Plant Verratrum californicum toxicity
- effects depend on stage of pregnancy exposed
Inflammatory conditions of bone (3)
Periostitis

Osteitis

Osteomyelitis
Periostitis
Inflammation of bone with the periosteum involved
Osteitis
General term for inflammation of bone, rarely used.
Osteomyelitis
Inflammation of bone with the medullary cavity involved
Non-infectious inflammation of bone
- how?
Single episode or repeated trauma

thus periostitis bc periosteum is involved
Possible routes of infection of bone (3)`
Haematogenous (embolic during septicaemia)

Direct implantation (penetrating trauma)

Local extension (from infected adjacent structure)
Why are growth plates vulnerable to haematogenous infection?
Fenestrated capillary loops (bendy bits slow down) in the metaphysis
4 steps in bone lesions dt bacterial infection (in detail)
1. Exudate + oedema > incr intramedullary pressure > ischaemia

2. Vascular stasis, infarction, toxic products (leukocytes, dying cells, bacterial toxins) > bone necrosis

3. Phagocytosis & osteoclastic resorption of necrotic bone, and/or

4. Necrotic bone remains as a sequestrum
Sequestrum & Involucrum
3 sequelae to osteomyelitis
(not including resolution)
Pathologic fractures

Growth disturbances, esp if physes involved

Damage to articular cartilage & extension into joints
Calf vertebral column.
What's this? Likely cause?
Vertebral ostemomyelitis and necrosis
Actinomyces pyogenes
Bovine vertebrae. Causative agent?
Hydatid cyst
Bovine mandible
Common name Correct name Causative agent
Lumpy jaw
Chronic pyogranulomatous osteomyelitis
Actinomyces bovis
Common infectious agents causing osteomyelitis
Viruses: BVDV, classical swine fever, canine distemper
Bacteria:
cattle: Actinomyces pyogenes, Actinomyces bovis
horses: Rhodococcus equi
Fungi: Aspergillus (dogs)
Protozoa: Leishmania (dogs)