Myopathy, GBS, Myaesthenia gravis

Question 1

What are the types of immune-mediated necrotising myopathies?

Answer 1

Anti-SRP
Anti-HMG-CoA-reductase
Antibody negative

CK is markedly elevated (in the several thousands)

Question 2

Histopathology of immune-mediated necrotising myopathy

Answer 2

Myofibre necrosis without inflammatory lymphocytic infiltrates

Question 3

What is overlap myositis?

Answer 3

Myositis in association with other connective tissue disorders

Question 4

What connective tissue disorders are associated with overlap myositis?

Answer 4

SLE, Sjogrens, RA, systemic sclerosis

Question 5

What are the histopathological findings of antisynthetase syndrome?

Answer 5

Perifascicular necrosis, perimysium fragmentation and increased ALP activity

Question 6

What is LEMS?

Answer 6

Lambert-Eaton Myasthenic Syndrome

- Caused by antibody to voltage-gated calcium channel

Question 7

What are the MRI findings of dermatomyositis?

Answer 7

On STIR sequence - hyperintensity or oedema in patchy distribution as well as oedema of subcutaneous tissue and fascia

Question 8

What antibodies are associated with dermatomyositis?

Answer 8

Anti:
Mi-2
TIF-1gamma
NXP-2
MDA-5
SAE

Question 9

What are the typical features of Dermatomyositis?

Answer 9

subacute onset of proximal muscle weakness accompanied or preceded by distinct rash

Question 10

What percentage of patients with LEMS have positive Antibodies for VGCC?

Answer 10

85%

Question 11

What are the histopathological findings in Dermatomyositis?

Answer 11

Perifascicular muscle fibre atrophy

Question 12

What are the findings in LEMS with repetitive stimulation?

Answer 12

Decrement with low rates (3Hz)

Increment with fast rates (20-50Hz)

Question 13

What are the signs of LEMS?

Answer 13

1. Areflexia/hyporeflexia
2. Autonomic dysfunction
3. Skeletal muscle weakness

Question 14

What are the different inflammatory myopathies? (6)

Answer 14

1. Dermatomyositis
2. Anti-synthetase syndrome
3. Immune-mediated necrotising myopathy
4. Overlap myositis
5. Polymyositis
6. Sporadic inclusion body myositis

Question 15

What are the different types of myopathy? (broad categories)

Answer 15

1. Neuromuscular junction disorders

2. Myopathies

Question 16

What is the clinical presentation of antisynthetase syndrome?

Answer 16

Some or all of:
Inflammatory myopathy
Interstitial lung disease
Arthritis
Raynaud syndrome
Fever
Mechanic hands

Question 17

What demographic is typically affected by LEMS?

Answer 17

Male predominance
Aged 50s or 60s
Associated with SCLC (Smokers)

Question 18

What are the nerve conduction study findings in LEMS?

Answer 18

low baseline amplitude

increased amplitudes after brief exercise

Question 19

What percentage of people with Anti-Jo1 Ab develop myositis?

Answer 19

90%

Question 20

What are some NMJ disorders? (4)

Answer 20

Botulism
myasthenia gravis
congenital myasthenic syndromes
Lambert-Eaton Myasthenic Syndrome (LEMS)

Question 21

What antibodies are associated with antisynthetase syndrome?

Answer 21

Anti-Jo1

Anti-PL-12

Question 22

What is the treatment for LEMS?

Answer 22

1. 3,4-diaminopyridine +/- pyridostigmine
2. IVIG or PLEX
3. Chronic immunosuppression may be required
4. Malignancy screening

Question 23

What are the typical features of an inflammtory myopathy?

Answer 23

Symmetrical, proximal weakness
With progression may involve truncal muscles
Myalgia or muscle tenderness may occur

Question 24

What rash is associated with dermatomyositis?

Answer 24

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

Question 25

What are the different types of musculodystrophies?

Answer 25

1. Dystrophinopathy (Duchenne MD, Becker MD)
2. Limb-girdle MD
3. Congenital MD
4. Myotonic dystrophy
5. Facioscapulohumeral MD
6. Emery-Dreifus MD
7. Oculopharyngeal MD
8. Dropped head, bent spine syndrome

Question 26

CK levels in dermatomyositis

Answer 26

Often increased

Question 27

Histopathology of immune-mediated necrotising myopathy

myofibre necrosis without inflammatory lymphocytic infiltrates