MSK non neoplstic bone & cartilage

What does R, P and H represent?

reserve, proliferative and hypertrophic zones of the physis/growth plate

What are the biomarkers for bone and explain their levels

ALP - present in all tissue but mainly liver, kidney, placenta and bone. Raised in young animals and in animals with bone-forming tumours

Calcium - raised in diseases involving bone metabolism. Hypercalcaemia of malignancy.

Two examples of congenital chondrodysplasia in farm animals

Bulldog calves

Spider lamb syndrome

Cause, Gross and histo features of bulldog calves

Affects Dexters and other minatures

Caused by 2 different mutations in ACAN gene

Gross:

• aborted before 7th month of gestation. Small calves, short limbs, protruding mandible, domed head, cleft palate, normal size tongue protruding from mouth

Histo:

• lacks distinct growth plates

• densely packed chondrocytes in physeal cartilage with no orderly arrangement. Fibrillar eosinophilic intercellular matrix

Cause, gross and histo pathology of spider lamb syndrome

Affects Suffolk and Hampshire sheep.

Caused by autosomal recessive mutation of FGFR3 gene

Gross:

• long limbs and neck, shallow body, scoliosis/kyphosis of thoracic spine, concave sternum and other sternal deformities

• Valgus deformity of forelimbs causing knocked-kneed appearance

Histo:

• abnormal ossification centres in bone developed by endochondral ossification

What breeds of cat get osteochondrocysplasia, its cause and gross and histo pathological features

Scottish fold, American curl

Autosomal dominant fold-eared gene

Gross:

• irregular size and shape of tarsal, carpal., metatarsal, metacarpal, phalanges and caudal vertebrae

• secondary degenerative arthropathy

Histo:

• defective endochondral ossification in physes beneath articular cartilage

Signalment, pathogenesis and gross and histo pathology of physeal dysplasia in cats

Male overweight Siamese and Maine Coons

usually 2-4 years, older than expected age of physeal closure (7-9 months)

Unknown pathogenesis

Physeal dysplasia affects all growth plates but only proximal femur fractures (due to force)

Gross = avulsed head of femur

Histo: dysplastic growth plates = disorganised clusters of chondrocytes surrounded by abundant matrix

Gross and histo pathology of osteogenesis imperfecta. What is the pathogenesis.

Gross:

• marked joint hypermobility causes inability to stand

• dentinogenesis imperfecta

• normal shape bones but very brittle

Histo:

• variable osteoblast numbers and activity

• calcified cartilage spicules in primary spongiosa lined by very thin layer of basophilic bone matrix

• little osteoclastic resorption or trabecular realignment. woven bone may line deeper secondary spongiosa

caused by collagen chain mutations in goldies and beagles (COL1A1 and COL1A2)

autosomal recessive mutation of SERPINH1 in dachshunds of collagen chaperone HSP47

Breed predisposition: holstein-friesians, charolais, angus, Romney lambs, the dog breeds mentioned above

Name this pathology and what causes it? Explain the pathogenesis. Describe the histology.

Lead line (band of sclerosis), caused by lead toxicity - a toxic osteodystrophy

Pathogenesis: impaired osteoclastic resorption. May contain acid-fast intranuclear inclusions.

Histo = persistence of mineralized cartilage trabeculae in the metaphysis

Cause of this toxic osteodystrophy in a cat. Explain the pathogenesis and gross and histo appearance.

Vitamin A toxicity, seen in cats fed liver.

Pathogenesis:

• inhibition of chondrocyte proliferation and reduction in RNA and protein synthesis

Gross hallmark = osteophyte formation = deforming cervical spondylosis

Histo

• physeal lesions = reduced chondrocyte proliferation = narrow growth plates

• osteoporosis = decreased osteoblasts and thinner osteoid seams

What is this condition and explain its pathogenesis. Describe the main gross and histo features.

Rickets = defective endochondrial ossification

Caused by insufficient dietary phosphorous or calcium/inappropriate ratio of the two, insufficient availability of activated vitamin D.

Gross:

• bowed legs, swollen joints. mostly at sites of rapid growth (long bone metaphysis, costochondral junction = rachitic rosary)

Histo:

• hypertrophic chondrocytes at physes and beneath articular cartilage = hallmark

Compare the histology of rickets and osteomalacia

Rickets shows pathology in the growth plates, while as osteomalacia affects adults it involves points under the most mechanical stress, such as where tendons intersect. These areas show localised accumulation of osteoid too.

What is this condition? Explain its pathogenesis. Describe the main gross and histological pathology.

Fibrous osteodystrophy

Pathogenesis: Persistently elevated parathyroid hormone (usually secondary to chronic renal disease or calcium/phosphorous dietary imbalance) eventually leads to generalised bone resorption.

Herbivores on high bran/concentrate diet, or carnivores on meat and offal only diets.

Gross: bilateral enlargement of skull bones, including maxilla and mandible

Histologically has 3 key features:

1. osteoclastic bone resorption

2. fibrosis

3. osteoblastic deposition of new woven bone

Cause of mandibular osteomyelitis in calf. Describe the gross and histological features.

Actinomyces bovis bacteria

Gross = honeycomb appearance due to pockets of inflammation surrounded by reactive bone

Histo = A.bovis colonies surrounded by Splendore-Hoeppli material, suspended in neutrophilic exudate

What is the cause of atrophic rhinitis in pigs and describe the pathogenesis.

Pasteurella multocida and Bordetella bronchiseptica produce toxins

Toxins inhibit osteoblast differentiation and stimulate osteoclastic activity = bone loss

What bacteria are involved in vertebral osteomyelitis in large animals? what is the most common?

Trueperella pyogenes = most common

Staphylococcus aures = invades osteoblasts

E.coli

Salmonella enterica Typhimurium

Fusobacterium necrophorum

Mannheimia haemolytica ….

Haematogenous infection of bone is the most common

Pathogenesis of avascular necrosis of the femoral head and its gross and histo features.

Affects westies aged 4-8 months

Pathogenesis = autosomal recessive trait

• ischaemia = delayed incorporation of blood vessels into femoral head

Gross = fracture and collapse of necrotic trabecular bone, and flattened femoral head

Histo = subchondral epiphyseal osteonecrosis