Path Musculoskeletal Flashcards
Describe what you would observe histologically in muscle necrosis ?
Histological signs of Myonecrosis
This often occurs segmentally
- poly or monophasic
- hypercontraction
- hyaline degeneration
- mineralisation
- leukocytes infiltration
- If the basal lamina remains intact and only mild damage may repair
Describe the pathological and clinical signs of muscle disorders ?
Signs of a muscle disorder
Pathology
Changes can be measured in the blood
- CK Creatine kinase
- AST Aspartate aminotransferase
- LDH Lactate dehydrogenase
- ALT Alanine aminotransferase
- Pallor; necrosis, minerlisation, fat infiltration
- Dark red/ black colour Haemorrhage, congestion
- Green colour eosinophilic inflammation, severe putrefaction.
Clinical signs
Atrophy, hypertrophy, swelling, weakness, spasm, oesophageal dysfunction (dogs and camilids) and abnormal gait.
Describe the three important factors when collecting a histopathological sample for diagnosis ?
Muscle biopsy
- Longitudinal and transverse
- Fixed and frozen sections
- Special stains
Best practice to pin muscle sample to prevent contraction during freezing.
Describe five factors which may lead to muscle atrophy ?
Pathology of muscle atrophy
- Denervation; common marked rapid atrophy (equine laryngeal hemiplegia, radial nerve paralysis in dogs HBC).
- Disuse - severe lameness, casts/ splints
- Malnutrition and cachexia - starvation, neoplasia and renal disease
- Endocine disorders - hypothyroidism HAD (Cushing’s)
- Congenital Myopathies
Identify this lesion and describe its pathology ?
Equine laryngeal hemiplegia
Denervation of the left recurrent laryngeal nerve
* Roarers in horses
* lack of laryngeal innervation
* restriction of respiratory flow
Describe what you would observe on a histological level in a case of muscle atrophy ?
Histology of muscle atrophy - chronic myopathies
- Fibre size variation
- Internal nuclei
- Vacuolation
- Fibrosis
- Fatty Infiltration
Provide three clear examples of disease which results in degenerative muscle disease ?
Muscle degenerative diseases
Ischaemic and Infarction (reperfusion injury)
- Occlusion of a major artery
- Aortic thromboembolism in cats, horses
- External pressure = Downer cows, recumbancy.
Nutritional Myopathy “white muscle disease”
- pictured below
- - selenium and vitamin E deficiency
- muscle very sensitive to loss of antioxidant defence
- cattle, sheep and horse; especially in young animals.
Toxic Myopathies
Exertional myopathies
Trauma
Provide examples of toxic myopathies which lead to muscle degenerative disease ?
Degenerative muscle disease
Toxic Myopathies
Ionophores - Monensin
- especially livestock
- horses are extremely susceptable
Plant toxins
Gossypol (cottonseed)
Cassia occidentalis
Identify this lesion and describe its pathology ?
Exertional Rhabdomyolysis
(degenerative muscle disease)
Tying up; Azoturia
Exercise induced muscle injury
- necrosis (lysis) of skeletal muscle = myolysis
- myoglobinuria and renal damage
- esp common in horses, greyhounds and wildlife capture myopathy
- associated with Se/vitE deficiency, PSSM in horses.
Describe the clinical signs and pathology of common bacterial myositis ?
Muscle inflammation: Bacterial Myositis
Pathology and Clinical signs
Clostridium perfringens, septicum and Chauvoi
- Usually secondary to penetrating wounds, injection sites, puncture wounds
- gas gangrene
- haemorrhage
- oedema
- necrosis
- esp ruminants, horses and pigs
Actinobacillus ligniersii
- Wooden toungue in cattle
- lumpy jaw infection
Provide examples of viruses which result in muscle myositis ?
Muscle myositis
Viruses
Bluetoungue vasculitis in sheep
Encephalomyelitis virus in pigs
Provide three examples of parasites which result in myositis ?
Parasitic myositis
Sarcocystis spp
- many species affected
- often no or little inflammation
- occ eosinophilic myositis in cattle (hypersentivity)
Neosporum caninum (dogs and foetal calves)
- bitches carriers - transmitted in utero
- puppy myositis and radiculoneuritis
- progressive denervation atrophy of pelvic limbs
Trichinella spiralis (pigs)
ecomomic importance, zoonotic
Provide examples of disesease which result in immune mediated myositis ?
Pathology immune mediated myositis
Dogs
- Polymyositis
- Masticatory myositis
- Extraocular myositis
Cats
- FIV
Horses
- Strep equi
- Equine influenza
Clinical signs
- Cytotoxic lymphocytes infiltrate the muscle
- interstitual and perivascular
Identify this lesion and describe its pathology ?
Canine Masticatory Myositis
(Eosinophilic myositis / Atrophic myositis)
Swelling and pain in the temporalis and masseter muscles
- inability to open jaw if severe
- bilateral symmetrical atrophy
- variable inflammation, necrosis and fibrosis
- lymphocytes and plasma cells or predominantly eosinophils
Identify this lesion and discuss its pathology ?
Canine X-linked muscular dystrophy
(inherited progressive degenerative muscle disease).
Clinical signs
Severe cases
- progressive weakness, die within a few days
Less severe cases
- stiff short gait develops at 2-3 months of age
- progressive weakness and muscle atrophy, splayed legs
- megaoesophagus
- spiration pneumonia
Provide two examples of inherited metabolic conditions of muscle ?
Inherited metabolic conditions of muscle.
(reduecd energy production in muscles, exercise intolerance, cramps and rhabdomyolysis).
Steatosis (lipomatosis)
- common in pigs and cattle
- fatty infiltration of muscle
Polysaccharide storage myopathy (PSSM)
- Horses QH, warm bloods and arabs
- recurrent exertional rhabdomyolysis (muscle break down)
- unexplained lameness, weakness and recumbancy etc
Disorders of glycogen metabolism, FA metabolism and mitochondrial function.
What is the pathology underlying Myotonia in goats ?
Myotonia in goats
(goat experiences tetanic muscle contraction when startled)
Channelpathies (sposmodic contractions)
- inherited myotonia in goats (defective chloride channel)
- chow chows, mini schnauzers, staffys
Describe the clinical signs and pathology of malignant hyperthermia ?
Malignant hyperthermia = porcine stress syndrome
pigs, horses and dogs
Pathology
- this is a genetic defect in muscle ryanodine receptor
- unregulated realese of calcium from the sarcoplasmic reticulum
- causes excessive myofibre contraction
- triggered by GA (halothane) or stress
Clinical signs
severe increase in body temperature
- often fatal
- pale soft exudative pork
Provide examples of how an electrolyte imbalance may lead to muscle weakness ?
Electrolyte disturnances and muscles
Hyperkalaemic periodic paralysis
- Inherited disorder of quarter horses (originates from a quarter horse stallion).
- very well defined muscle groups “impressive”
- membrane instability and transient increased excitability
- Hyperkalaemic = toomuch potassium in the blood stream.
Hypokalaemia, Hypernatremia
- Hypokalaemia = deficiency of potassium in the blood stream
- Hypernatremia = rise in serum sodium concentration
- muscle weakness in many species
Hypocalcaemia, Hypophosphataemia
- Hypocalcaemia low serum concentrations of calcium
- Hypophosphataemia low phosphate in the blood
- muscle weakness in many species
Provide examples of neuropathic conditions (those which causes denervation of muscles) ?
Neuropathic conditions
(cause denervation of muscles)
Peripheral neuropathy
- trauma (radial nerve, recurrent laryngeal nerve)
- toxins (Stringhalt in horses, lead)
Motor neuropathy
- Vitamin D deficiency: equine motor neuron disease
- Sarcocystis neurona: horses
Provide three examples of neuromuscular junction disorders ?
Neuromuscular junction disorders
Botulism
- Clostridium botulinum toxin
- blocks the release of Ach irreversibly
- profound generalised muscle paralysis, slow recovery death
Tick paralysis
- Ixodes holocyclus
- Toxin blocks the release of Ach reversibly
- progressive paralysis but rapid recovery with antitoxin
Myasthenia gravis
- Congenital or acquired (immune mediated)
- acquired is linked abnormalities eg thyoma
- lack of activation of Ach receptors by autoantibodies
- progressive muscle weakness and collapse
Define the metaphysis, epiphysis, diaphysis and epiphyseal plate ?
Describe the ways in which bone reacts to injury ?
Reaction of bone to injury
Remodelling
- osteopaenia/ atrophy, osteosclerosis
Disruption to endochondral Ossification
- growth arrest lines, growth retardation lattace ( lack of trabeculae), premature closure of growth plates
- periosteal bone formation
- fractures
- inflammation.
Identify this lesion and describe its pathology ?
Osteopaenia
(bone remodelling atrophy)
Osteopaenia = decreased bone per unit area
Example
Foal in plaster for two months (increased bone resorptions and decreased bone formation).
Identify this lesion and describe its pathology ?
Ostesclerosis
(bone remodelling)
Osteosclerosis = increased bone per unit of area
Pathology
- response to increased mechanical stress
- example; osteosclerosis due to degeneration and loss of intervertebral discs between these vertebrae.
Identify this lesion and describe its pathology ?
Growth arrest lines
Growth arrest lines occur due to slowed growth
- lines occur parallel to the growth plate in metaphysis
- occurs due to multiple nutrient deficiencies.
Describe how a joint may respond to injury ?
The response of the joint to damage
- Inflammation (intra-articular enzymes and cytokines may cause degeneration).
Synovitis - synovial villous hyperplasia
*Pannus development of fibrovascular tissue - Increased lubrication (cytokines in synovial fluid can cause degeneration of cartilage)
- Periarticular osteophytes (bone deposition around joint edges).
- Sclerosis - subchondral bone
The joint has a minimal capacity to repair
- superficial erosions persist for long periods
- ulcerations down to the subchondral bone are filled with vascular fibrous tissue (may become fibrocartilage)
Identify this lesion and describe its pathology ?
Synovial villous hyperplasia
- synovitis
- hip dysplasia
Identify this lesion and describe its pathology ?
Pannus
The development of fibrovascular tissue.
- may cause fibrous ankylosis (fusion of the joint)
Identify this lesion and describe its pathology ?
Periarticular Osteophytes
Bone deposition around the edges of joint
Accompany degenerative articular changes
- joint instability eg hip dysplasia
Identify this lesion and describe its pathology ?
Osteochondroses = retention of cartilage
Lesions in growth cartilage of young animals
- common pigs, dogs, horses and poultry (especially those bred and fed to grow rapidly).
- Failure or delay of endochondrial ossification
- retention of cartilage due to a failure to become minerlised
- metaphyseal growth plate
- AECC complex (growth plate beneath articular cartilage)
- accumulation of hypertrophic chondrocytes
May cause secondary adjacent haemorrhage and necrosis.
Identify this lesion and describe its pathology ?
Osteochondritis dissecans.
Dysplasia of the articular epiphyseal cartilage complex
This usually occurs secondarily to osteochondrosis
- forms clefts in the retained cartilage
- fracture of the overlying articular cartilage
Cartilagenous or osteochondrial flap
- if flap breaks and becomes free within the joint = joint mouse
Clinical signs
- pain (lameness)
- synovitis
- joint effusion
Identify this lesion and discuss its pathology ?
Cervical vertebral myelopathy
Stenosis of the cervical vetebrae
This is growth and developmental abnormalities.
- compression of the spinal cord
- static compression of cervical vertebrae 5,6,7
- dynamic compression when the neck is flexed
- wallerian degeneration
- Horses, giant bred dogs
This causes a syndrom in horses known as “Wobbler”
Identify this lesion and describe its pathology and clinical signs ?
Hip dysplasia
(Developmental abnormality)
Pathology
- major problem in dogs
- overweight, overexercised and hereditary
Clinical signs
Early hip joint laxity
- instability, shallow acetabulae
Chronic subluxation
- partial dislocation of the joint
Severe secondary DJD
- cartilage erosion / ulceration
- marked bone remodelling and osteophyte formation
Identify this lesion and describe its pathology ?
Osteopetrosis
(Growth and developmental abnormality)
Osteosclerotic disease (increased bone density)
Failure of osetoclasts to resorb and shape primary trabeculae
- primary trabeculae fill the medullary cavity
- no medullary cavity
- rare dogs, sheep, horses and cattle
Identify this lesion and describe its pathology ?
Craniomandibular Osteopathy “lion jaw”
Hypertrophic osteopathy
- thickened mandibles, occipital and temporal bones
- WHW terriers 6 months may regress
Identify this lesion and describe its pathology ?
Chondrodystrophies
(Growth and developmental abnormalities).
This can result in dwarfism
- The primary lesions in growth of cartilage (inherited)
- disorders of endochondrial bone growth
- small limbs
- normal sized head (membranous bone)
Define the terms Epiphysiolysis and Arthrogryposis ?
Growth and developmental disorders.
Epiphysiolysis
- seperation of the epiphysis from the metaphysis
- Un-united anconeal process of the ulna (dogs)
- Femoral head (heavy cats)
Arthrogryposis
Congenital contracture of joints
- usually bilaterally symetrical
- sporadic unknown cause
- intrauterine infections (Akabane, Bluetoungue virus)
- some plant toxins
Describe the pathology of Osteopaenia and Osteoporosis ?
Metabolic bone diseases
Osteopaenia
- reduced mineral content of bones
- reduced bone mass
- porous, thin and brittle bones
Osteoporosis
This is a clinical disease of bone pain and fracture caused via osteopaenia
- Ca deficiencys
- glucocortcoid therapy
- physical inactivitys
- starvation
What is the difference between Rickets and Osteomalacia ?
Metabolic bone diseases
Rickets
Affects young animals both bone and cartilage (endochondral oss).
Osteomalacia
Affects adults and bone only
Describe the pathology and clinical signs of osteomalacia and Rickets ?
Rickets and Osteomalacia
Metabolic bone diseases
Pathology
This is the defective mineralisation of bone and accumulation of osteoid
Cause
- vitamin D deficiciency
- phosphorous deficiency
- lack of sunlight
Clinical signs
- bone pain
- pathological fractures
- deformaties (scoliosis)
Identify this lesion and describe its pathology ?
Fibrous osteodystrophy
(metabolic bone disease)
Bone mass reduced due to resorption and replacement by fibrous tissue
This is caused by hyperparathyroidism.
Describe the four different types of Fibrous atrophy ?
Fibrous atrophy = hyperparathyroidism
(metabolic abnormality causing reduced bone mass and replacement with fibrous tissue).
Primary (rare)
Functional parathyroid tumour
Paraneoplastic
PTH- like protein (anal adenomas)
Secondary nutritional
Low CA, high phosphorous diet
Secondary renal
Failure of kidney to secrete phosphorous
What would we observe when bone becomes inflammed ?
Inflammation of bone and bone marrow = Osteomyelitis
This is a common problem in neonatal production animals; and foals
Necrosis of bone and reabsorption along with a compenastory production of new bone
- pathological fractures
- fistulae
- sequestrum
- - thrombosis
- infarction
- ostecalst may relaese enzymes and inflammatory cytokines
Identify common causes of bone inflammation Osteomyelitis
Pathology of Osteomyelitis
Arcanobacterium pyogenes
Strep spp
E.coli sp
Staph sp
Salmonella sp
Actinomyces bovis - lump jaw
Identify this lesion and describe its pathology ?
Hypertrophic osteodystrophy
(Non infectious inflammation of bone).
The causes remains unknown
Usually young rapidly growing dogs
Metaphyseal osteopathy
- suppurative, fibrinous inflammation and necrosis of the metaphyses
- metaphyseal periosteal new bone
Clinical signs
Lameness
fever
swollen and painful metaphyses of long bones
Identify this lesion and describe its pathology ?
Panosteitis
(non infections inflammation of bone).
Young large breed dogs - cause is unknown
- Increased densities in the medullary cavities
Clinical signs
- Self limiting painful disease (lameness)
Describe the pathology underlying legg-calve-perthes disease ?
Legg-calve-perthes Disease
(Avascular (ischaemic) necrosis of bone).
This causes infarction of the femoral head
- collapse of articular cartilage secondary to resorption of necrotic subchondral bone
- non septic
- young, small miniture breeds
Define the terms Arthropathy, synovitis and arthritis ?
Definitions
Arthropathy = Any type of joint disease
Synovitis = inflammation of the synovium only
Arthritis = inflammation of the synovium and lesions in articular cartilage.
Describe the pathology and clinical signs of infectious Arthritis ?
Infectious Arthritis
(neonatal septicaemia commonly causes polyarthritis)
Pathology
- Mycoplasm arthritis
- Caprine encephalitis virus (CAE)
Clinical signs
Inflammation of the synovium and articular cartilage
- erosions and ulceration develop over time
- synovial hyperplasia
- hypertrophy
- pannus formation = abnorma fibrovascular layer of granulation tissue
Provide an example of non - infectious (sterile) arthritis ?
Identify this lesion and describe its pathology ?
Osteoarthritis / Osteoarthrosis
Desstructive disease of the articular cartilage in the joint
Pathology = variety of diseases with the same end point
Loss of proteoglycans - chondromalacia - surface erosions - frayed appearance - ulceration - exposure of the subchondral bone.
- synovitis
- osteophyte formation
- remodelling of bone
Clinical signs
- joint enlargement
- deformity and mulfunction
- pain
Identify this lesion and describe its pathology ?
Invertebral disc disease
(Degenerative prolapsed invertebral disc and spondylosis, ankylosing)
Pathology
Caused by mechanical instability or excess mechanical force on the intervertebral disc joints.
Clinical signs
Spondylosis = Degenerative change in vertebrae involving periosteal formation on the ventral and lateral periosteal surfaces
Ankylosis = abnormal stiffening and immobility
Define osteophytes, Hyperostosis and Enthesiophyte ?
Identify this lesion and describe its pathology ?
Osteochondromas
Inherited defect in skeletal development
Multiple cartilagenous exotoses
Exotoses = a benign outgrowth of cartilage in bone.
- protrude from bony surfaces adjacent to physes (long bones, ribs, vertebrae)
- appear soon after birth (pups, foal)
- growth may cease at maturity
Identify this type of neoplasm ?
Chondrosarcoma
Identify this type of neoplasm ?
Osteosarcoma
Identify this neoplasm ?
Synovial cell sarcoma
