58 Musculoskeletal 3

Question 1

Which investigations are use in muscle diseases? (5).

Answer 1

Clinical exam.
Electromyograph.
Nerve conductions studies.
MRI.
Serum/Blood investigations.

Question 2

Name two diseases of the basal lamina:

Answer 2

Merlin deficiency.

Integrin VII deficiency (limb girdle syndrome).

Question 3

What is motor neurone disease?

Which cells does it involve? (3).

Answer 3

Widespread degeneration of motor neurones.

Anterior horn cells, brain stem nuclei, Betz cells.

Question 4

What are the signs of motor neurone disease? (4).

Answer 4

Fasciculation.
Wasting.
Spasticity.
Brisk reflexes.

Question 5

Which gene is responsible for spinal muscular atrophy?

What is the course of SMA?

Answer 5

SMN1 gene.
Begins very young to aged 15.
3 severities: very early death to adult survival with disability.

Question 6

What is the genetic and molecular basis of Duchenne muscular dystrophy?

Answer 6

X linked recessive disorder.

Dystrophin protein - uncontrolled Ca entry into cell.

Question 7

When and how does Duchenne muscular dystrophy present?

Answer 7

2-4 years of age.

Proximal muscle weakness with calf muscle hypertrophy. Elevated CPK.

Question 8

What is the prognosis for Duchenne muscular dystrophy?

Answer 8

Wheelchair by 12.

Dead by 25 due to cardiomyopathy.

Question 9

What is Becker dystrophy?

Answer 9

Variant of DMD, with later onset and slower progression.

Question 10

Which proteins are affected in limb girdle dystrophy? (3)

Answer 10

Nuclear membrane related proteins.

Emerins, laminin A/C.

Question 11

What is limb girdle dystrophy?

Genetic basis?

Answer 11

Dystrophy of pelvic/shoulder girdle.

Autosomal recessive condition.

Question 12

What is the genetic defect seen in facioscapulohumeral dystrophy?
Fibre changes?

Answer 12

Large telomeric deletion.
Autosomal dominant.
Angular, atrophic fibres.

Question 13

What are the effects of facioscapulohumeral dystrophy?

Associated with?

Answer 13

Weakness of face + shoulder.

Progressive deafness, retinal vasculopathy.

Question 14

What is the genetic basis of myotonic dystrophy?

Answer 14

CTG repeat expansion in X19.

Autosomal dominant.

Question 15

When is the onset of myotonic dystrophy?

What are the effects? (4)

Answer 15

Onset 20-30 years.
Weakness of face, limb girdle + proximal muscles.
Myotonia (persistent contraction after voluntary effort has ceased).

Question 16

What are the histological changes seen in myotonic dystrophy? (4)

Answer 16

Type 1 fibre atrophy.
Type 2 fibre hypertrophy (compensation).
Central nuclei.
Motheaten, targetoid + ring fibres.

Question 17

What is polymyositis?

How does it present?

Answer 17

Inflammatory muscle disorder.

Weakness, pain and swelling of proximal muscles.

Question 18

What is dermatomyositis?

Answer 18

Complement deposition in capillaries causes muscle ischaemia.

Question 19

What are the histological findings in polymyositis and dermatomyositis?

Answer 19

Perimysial inflammation with B cells.

Endomysial inflammation with T cells.

Question 20

How is polymyositis treated?

Answer 20

Corticosteroids and azathioprine.

Question 21

What is inclusion body myositis? (3)

Answer 21

Clinically like polymyositis. But…
Shows filamentous intracellular inclusions.
Responds poorly to corticosteroid + azathioprine.

Question 22

How do congenital myopathies present? (2)

Name two:

Answer 22

Hypotonia + floppiness in infancy.
Congenital fibre type disproportion.
Congenital nuclear myopathy.

Question 23

What is the cause of malignant hyperthermia?

Answer 23

Prolonged rise in intracellular calcium ions.

Question 24

How does myasthenia graves present?

Age/sex, effects (3)

Answer 24

Female 20-30.

Fluctuating weakness affecting ocular, bulbar and proximal muscles.

Question 25

What is the molecular basis of myasthenia graves?

What is it commonly associated with?

Answer 25

IgG against ACh receptor proteins.

Thymus hyperplasia.

Question 26

What is Lambert-Eaton myasthenic syndrome?

How does it present?

Answer 26

Paraneoplastic disorder associated with small cell carcinoma of lung (oat cell cancer).
Weakness of proximal muscle and girdles.

Question 27

What is the molecular basis of Lambert-Eaton myasthenia syndrome?

Answer 27

IgG binds to pre-synaptic calcium channels, preventing release of ACh.

Question 28

What changes are seen on muscle biopsy in myasthenia syndromes?

Answer 28

No specific/little changes.

Question 29

Where are muscle biopsies taken from? (3).

Answer 29

Deltoid.
Biceps.
Quadriceps.

Question 30

What is core disease:
Genetics:
Histology:
Presentation?

Answer 30

Autosomal dominant.
Cores of inactivity to NADH-Tr in type 1 fibres.
When child starts to walk.

Question 31

How does nemaline myopathy present? (4)

Genetics?

Answer 31

Neonatal hypotonia.
Respiratory insufficiency.
High arched palate.
Kyphoscoliosis.

Autosomal recessive.

Question 32

What histological changes are seen in mitochondrial myopathies?

Answer 32

Whorled cristae.

Accumulation of lipid on Oil Red O stain.

Question 33

Which drugs can induce myopathy? (3).

Answer 33

Statins.
Steroid.
Heroin/ecstasy:

Question 34

What type of myopathy does heroin and ecstasy precipitate?

Features? (3).

Answer 34

Acute necrotising myopathy.

Rhabdomyolysis.
Myoglobinuria.
Renal failure.