Muscle pathology Flashcards
What is the epimysium?
The fibrous sheath which surrounds the entire skeletal muscle
What is the endomysium?
The fibrous sheath which surrounds individual muscle fibres
What is the perimysium?
The fibrous sheath which surrounds groups of muscle fibres to create a fascicle
What are the indications for muscle biopsy?
Evidence of muscle disease - weakness, atrophy, raised CK
Presence of neuropathy
Presence of vascular disorder
What histological changes might be seen in muscular dystrophy?
Variability in size of muscle fibres Endomysial fibrosis Fatty infiltration Increased central nuclei Segmental necrosis
What are muscular dystrophies?
A group of inherited diseases that cause progressive weakening of muscles
What is the pathophysiology of muscular dystrophies?
There is destruction of single muscle fibres in the muscles, which are then regenerated
This causes fibrosis of the muscles
When does Duchenne Muscular Dystrophy typically present?
2-4 years old
What is the pathophysiology of Duchenne muscular dystrophy?
There is a mutation of the dystrophin gene on the long arm of chromosome X
Actin fibres don’t adhere properly to the basement membrane, leaving fibres liable to tearing
There is uncontrolled Ca2+ entry into cells
What is myositis ossificans?
A condition where heterotopic ossification (bone forming outside the skeleton) occurs in muscles usually after an injury
What are polymyositis and dermatomyositis?
Idiopathic inflammatory myopathies
Which gender do polymyositis and dermatomyositis affect?
Female:male 2:1
What is the peak age of incidence in polymyositis and dermatomyositis?
40-50
What are patients with polymyositis and dermatomyositis at increased risk of?
Malignancy, particularly dermatomyositis (15%)
Lung, breast, ovarian, stomach, colon and bladder
Which patients with polymyositis and dermatomyositis in particular are at risk of malignancy?
Men >45
What cutaneous signs may be present in dermatomyositis?
Gottrons sign (fingers and knuckles)
Heliotrope rash
Shawl sign
What other organs may be involved in polymyositis and dermatomyositis?
Lungs: respiratory muscle weakness and interstitial lung disease, breathlessness, cough
Heart: myocarditis
Oesophagus: dysphagia
What general systemic symptoms may be present in polymyositis and dermatomyositis?
Fever
Weight loss
Raynaud’s
Non-erosive polyarthritis
What other diseases are polymyositis and dermatomyositis associated with?
Diabetes mellitus
Thyroid disease
What drugs are development of polymyositis and dermatomyositis associated with?
Steroids
Statins
What tests on examination can be done to investigate polymyositis and dermatomyositis?
Confrontational testing - direct testing of power
Isotonic testing - 30 second sit to stand test
What blood tests should be done to investigate polymyositis and dermatomyositis?
Creatine kinase
Inflammatory markers
Electrolytes, calcium, PTH, TSH to exclude other causes
What auto-antibodies may be present in polymyositis and dermatomyositis?
ANA
Anti-Jo-1
What investigations should be done to confirm polymyositis and dermatomyositis?
Electromyography (EMG)
Muscle biopsy
MRI
What would be seen on electromyography in polymyositis and dermatomyositis?
Increased fibrillations
Abnormal motor potentials
Complex repetitive discharges
What would be seen in muscle biopsy in polymyositis and dermatomyositis?
Perivascular inflammation and muscle necrosis
What would be seen on MRI of polymyositis and dermatomyositis?
Muscle inflammation, oedema, fibrosis and calcification
What is the treatment for polymyositis and dermatomyositis?
Glucocorticoids Azathioprine Methotrexate Ciclosporin IV immunoglobulin
What is inclusion body myositis?
An inflammatory muscle disease, characterized by slowly progressive weakness and wasting of mostly distal, but some proximal muscles, most apparent in the muscles of the arms and legs
Which gender is inclusion body myositis most apparent in?
Males 3:1
At what age are patients affected by inclusion body myositis?
> 50
Which muscles are most commonly affected by inclusion body myositis?
Wrist and finger flexors in upper limbs
Quadriceps and anterior tibial muscles in legs
Which has higher levels of CK: polymyositis or inclusion body myositis?
Polymyositis
What is polymyalgia rheumatica?
Polymyalgia rheumatica (PMR) is a condition that causes pain, stiffness and inflammation in the muscles around the shoulders, neck and hips
At what age does polymyalgia rheumatica occur?
> 50
What condition is polymyalgia rheumatica associated with?
Giant cell arteritis
What are the symptoms of polymyalgia rheumatica?
Ache in shoulder and hip girdle
Morning stiffness
Fatigue, anorexia, weight loss and fever
Reduced movement of shoulders, neck and hips
Is muscle strength affected in polymyalgia rheumatica?
No
What is the treatment for polymyalgia rheumatica?
Low dose steroids
Gradual reduction at 18months - 2years
What is the commonest cause of musculoskeletal pain in women aged 22-50 years?
Fibromyalgia
What gender is fibromyalgia most common in?
Females 6:1
What may trigger fibromyalgia?
Emotional or physical trauma
Is fibromyalgia associated with inflammation?
No
What are the clinical manifestations of fibromyalgia?
Chronic pain: neck, shoulders, lower back, chest wall
Varies in intensity
Symptoms worse with exertion, fatigue and stress
Sensation of swelling
Fatigue and poor, unrefreshing sleep
Pins and needles/tingling, headaches, depression, abdominal pain (IBS), poor concentration and memory
What is the treatment for fibromyalgia?
Patient education Graded exercise programme Cognitive behavioural therapy Complementary medicine eg. acupuncture Antidepressants Analgesia e.g. tramadol Gabapentin and pregabalin
