Myopathies Flashcards
Myopathy history
Negative symptoms
-weakness (functional issues)
-fatigue
-exercise intolerance
-atrophy
Positive symptoms
-hypertrophy
-cramps
-contractures
-stiffness
-myotonias (inability to relax)
-myalgias
-myoglobinuria
Time course
-acute, subacute, chronic
-fluctuating, episodic
-progressive, static
-childhood or adult onset
Systemic illness
-rheumatological: joint pain/swelling, rash, fever, weight loss
-genetic: cataracts, frontal balding, hormonal issues, cardiac issues
-mitochondrial: mental impairment, seizures, dysmorphism, scoliosis
Family history
-problems with walking, working, arm strength
-pattern of inheritance
Triggers
-drugs (prescribed and illicit)
-anaesthetics
-illness and fever
-exercise
-diet
Myopathy investigations
Bloods
-CK (usually elevated)
-urine myoglobin
-AST/ALT/LDH (may be elevated)
-K and Ca (may cause weakness)
-TFTs (possible cause of myopathy)
-ESR/ENA/ANA
-Specific antibodies
-Gene testing
Nerve conduction studies
-motor and nerve studies
-repetitive stimulation
-needle EMG
Muscle MRI
-increased STIR/T2 signal with inflammation
-fatty replacement with chronicity
Muscle biopsy
-equivocal or negative gene studies
Dermatomyositis features
Subacute onset
Proximal weakness
Accompanying or preceding rash
-photosensitive areas
-erythematous, oedematous, sometimes itchy
-heliotrope (purple/red upper eyelids)
-gottron sign (scaling, erythematous lesions over finger joints)
-mechanic hands (rough, cracked fingertips)
Extra muscular manifestations
-cardiac, pulmonary, GI, joints
-malignancy
Bloods
-Elevated CK and ANA
-Specific antibodies
Muscle histopath features
Muscle MRI features
Antisynthetase syndrome
Some or all of
Inflammatory myopathy
Interstitial lung disease
Inflammatory arthritis
Raynauds
Mechanic hands
Specific antibodies
Muscle histopathology
Immune mediated necrotising myopathy features
Acute or subacute
Severe proximal muscle weakness
Extra muscular involvement is rare
Very elevated CK
Specific antibodies
Minimal findings on muscle biopsy
Inclusion body myositis features
Older men
Slow progression
Preferential quads, ankle dorsiflexors, finger flexor weakness
Neck, facial and bulbar weakness possible
Reduced patellar reflex early
Mild CK rise
Specific antibodies
Muscle MRI
-Anterior thigh muscle involvement
Muscle biopsy findings
Overlap myopathy features
Systemic rheumatic disease
Mild muscle involvement
Mild CK rise
Specific antibodies
Polymyositis
Rare
Diagnosis of exclusion
Subacute proximal weakness
Myasthenia gravis overview
Epidemiology
-uncommon
-occurs at any age
Pathophys
-Autoantibodies to ACh receptor
-Blockade, internalisation and destruction of AChR
General features
-Ocular or generalised disease
-Fluctuating and fatiguing weakness improving with rest
-Progression over years
Diagnosis
-Antibodies
-Repetitive stimulation
-Single fibre EMG
-Ice pack test
-CT for thyoma
Treatment
-IVIg and PLEX for exacerbations
-Pyridostigmine
-Steroids
-Immunosuppression
Ocular features
-Pupillary function always normal
-Ptosis (fatigued upward gaze and ice pack sign)
-Diplopia with fatiguing (resolves with one eye closed)
Bulbar features
-fatiguing dysarthria and hypophonia
-dysphagia and jaw weakness
-expressionless, weak facial muscles, myasthenic sneer
Neck and limb features
-neck flex/extensor weakness
-proximal limb weakness (arms more than legs)
Respiratory features
-decreases FVC
-respiratory failure in myasthenic crisis
Myopathy exam
Weakness
-generalised/focal
-proximal/distal/mixed
-symmetric/asymmetric
-ocular, bulbar, neck, respiratory involvement
-gait
-function
Additional
-hypertrophy, atrophy
-contractions, stiffness
-dysmorphism
-systemic illness