Myopathy, GBS, Myaesthenia gravis Flashcards
What are the types of immune-mediated necrotising myopathies?
Anti-SRP
Anti-HMG-CoA-reductase
Antibody negative
CK is markedly elevated (in the several thousands)
Histopathology of immune-mediated necrotising myopathy
Myofibre necrosis without inflammatory lymphocytic infiltrates
What is overlap myositis?
Myositis in association with other connective tissue disorders
What connective tissue disorders are associated with overlap myositis?
SLE, Sjogrens, RA, systemic sclerosis
What are the histopathological findings of antisynthetase syndrome?
Perifascicular necrosis, perimysium fragmentation and increased ALP activity
What is LEMS?
Lambert-Eaton Myasthenic Syndrome
- Caused by antibody to voltage-gated calcium channel
What are the MRI findings of dermatomyositis?
On STIR sequence - hyperintensity or oedema in patchy distribution as well as oedema of subcutaneous tissue and fascia
What antibodies are associated with dermatomyositis?
Anti: Mi-2 TIF-1gamma NXP-2 MDA-5 SAE
What are the typical features of Dermatomyositis?
subacute onset of proximal muscle weakness accompanied or preceded by distinct rash
What percentage of patients with LEMS have positive Antibodies for VGCC?
85%
What are the histopathological findings in Dermatomyositis?
Perifascicular muscle fibre atrophy
What are the findings in LEMS with repetitive stimulation?
Decrement with low rates (3Hz)
Increment with fast rates (20-50Hz)
What are the signs of LEMS?
- Areflexia/hyporeflexia
- Autonomic dysfunction
- Skeletal muscle weakness
What are the different inflammatory myopathies? (6)
- Dermatomyositis
- Anti-synthetase syndrome
- Immune-mediated necrotising myopathy
- Overlap myositis
- Polymyositis
- Sporadic inclusion body myositis
What are the different types of myopathy? (broad categories)
- Neuromuscular junction disorders
2. Myopathies
What is the clinical presentation of antisynthetase syndrome?
Some or all of: Inflammatory myopathy Interstitial lung disease Arthritis Raynaud syndrome Fever Mechanic hands
What demographic is typically affected by LEMS?
Male predominance
Aged 50s or 60s
Associated with SCLC (Smokers)
What are the nerve conduction study findings in LEMS?
low baseline amplitude
increased amplitudes after brief exercise
What percentage of people with Anti-Jo1 Ab develop myositis?
90%
What are some NMJ disorders? (4)
Botulism
myasthenia gravis
congenital myasthenic syndromes
Lambert-Eaton Myasthenic Syndrome (LEMS)
What antibodies are associated with antisynthetase syndrome?
Anti-Jo1
Anti-PL-12
What is the treatment for LEMS?
- 3,4-diaminopyridine +/- pyridostigmine
- IVIG or PLEX
- Chronic immunosuppression may be required
- Malignancy screening
What are the typical features of an inflammtory myopathy?
Symmetrical, proximal weakness
With progression may involve truncal muscles
Myalgia or muscle tenderness may occur
What rash is associated with dermatomyositis?
Heliotrope rash - purple / red discolouration over skin of upper eyelids
V-sign (anterior chest) and Shawl sign - rash over photo-exposed areas
Grotton sign - scaling, erythematous eruptions covering bony prominences especially MCP, PIP, DIPs
Mechanic hands - rough, cracking appearance of fingertip skin
What are the different types of musculodystrophies?
- Dystrophinopathy (Duchenne MD, Becker MD)
- Limb-girdle MD
- Congenital MD
- Myotonic dystrophy
- Facioscapulohumeral MD
- Emery-Dreifus MD
- Oculopharyngeal MD
- Dropped head, bent spine syndrome
CK levels in dermatomyositis
Often increased
Histopathology of immune-mediated necrotising myopathy
myofibre necrosis without inflammatory lymphocytic infiltrates
