Muscular Dystrophies (FSHD, DMD/BMD, LGMD)

Question 1

Clinical features of FSHD

Answer 1

Winged scapula
Myopathic facies (also seen in myotonic dystrophy)
Facial muscle weakness
Upper limb girdle muscle weakness
Abdominal muscle weakness (Beevor's sign)
Foot drop, very late sign of LL weakness

A. Inspection and exposure - remove shirt, observe surroundings
1. Winged scapula at the back
2. Superior margins of scapulae visible from the front above the clavicles (UL girdle muscle wasting)
3. Myopathic facies WITHOUT frontotemporal balding
4. Facial muscle weakness
- Orbicularis oculi, oris and zygomaticus - difficulty with eye closure, smiling, whistling, pursing lips
- NO ophthalmoplegia (important negative)
5. Foot drop - scuffing at front of shoes, ankle/foot orthoses, walking aid, wheelchair bound

B. Feel and move
1. Wasting and weakness of upper limb girdle muscles and upper arms
- Shoulder weakness (scapula fixation) < 80% cases with relative sparing of deltoids (no weakness when scapula is stabilised manually against chest wall)
- Biceps and triceps weakness (sparing of forearm)

2. Arms out in front
   - Winged scapula more prominent (trapezius muscle weakness)
3. Abdominal muscle weakness
   - Lumbar lordosis, protuberant abdomen
   - Beevor’s sign: - at supine, flex neck/raise head
   (lower abdominal muscles weaker than upper, displacing umbilicus upwards)
4. Bilateral foot dorsiflexion weakness (anterior tibialis muscle) with foot drop
5. Lower limb girdle weakness (very late progression)

C. Wishlist
1. Hearing aid and assessment (75% sensorineural deafness)
2. Fundoscopy (60% retinal telangiectasia)

Question 2

Clinical features of DMD and BMD

Answer 2

~~~
Young patient with ambulatory deficit
Proximal to distal muscular dystrophy

A. Inspection and exposure
1. Young patient
- Duchenne - 20-25 years old
- Becker - 40-50 years old
2. Ambulatory status
- Wheelchair bound
- Or waddling gait - wide based gait with trunk moving from side to side, pelvis drops on each side when foot leaves the ground
3. Gower sign - uses knees to push up from lying to standing (due to hip extensor weakness)

B. Feel and move
1. Neck muscle wasting and weakness
- Neck flexors more affected than neck extensors

2. Proximal upper limbs weakness
   - Wrist extensors more affected than wrist flexors
3. Proximal lower limbs weakness
   - Tibialis anterior more affected than gastrocnemii and solei muscles
   - Pseudohypertrophy of calf muscles from fibrofatty infiltration of necrotic calf muscles and compensatory hypertrophy from anterior tibialis weakness
4. Contractures - Archilles tendon, hip, knee flexors
   - Associated scars of previous tendon surgeries
5. Reduced to absent deep tendon reflexes (from muscle fibre loss)

C. Severity and complications
1. Kyphoscoliosis - paraspinal muscle weakness
2. Inability to generate forceful cough - thoracic muscle weakness (respiratory failure)

D. Wishlist
1. Bedside spirometry - respiratory failure
2. Cardio exam
A. Displaced apex, MR murmur (dilated CM)
B. Right ventricular heave, loud P2 (pulmonary HTN)

Question 3

How would you differentiate DMD and BMD?

Answer 3

Question 4

Muscular dystrophies are a group of disorders of ____ due to degeneration of ____

Classically pattern of weakness: __

Answer 4

Progressive weakness
Skeletal muscle

Proximal to distal (with exceptions)

Question 5

What are examples of distal to proximal muscular dystrophies?

Answer 5

1. Oculoparhyngodistal myopathy
2. Distal myopathy (Welander, Finish, Markesbury, Miyoshi, distal nebulin)
3. Inclusion body myopathy
4. Myopathy with ringed muscle fibres
5. Limb girdle muscular dystrophy type 2B

Question 6

Genetics of muscular dystrophy

Answer 6

FSHD
- Autosomal dominant (80%), others sporadic
- Chromosome 4q35

DMD and BMD
- X linked recessive - dystrophin gene Xp21
- Son 50% affected, daughter 50% carriers
- Loss of dystrophin causes sarcolemmal breakdown, calcium influx into muscle cells, oxidative stress and injury, muscle cell death

Question 7

Other muscular dystrophies

Answer 7

1. Emery-Dreifuss muscular dystrophy
   - Scapulo-humero-peroneal wasting with winging of scapula, weakness
   - Early contractures of elbow, ankle, neck
   - Cardiac conduction defects
2. Oculopharyngeal muscular dystrophy
   - Slow progressive ptosis
   - Dysphagia
   - Dysarthria
   - Frontalis overactivity and overextension of neck as compensation
3. Limb girdle muscular dystrophy
   - Progressive weakness of shoulder and pelvic girdle muscles
   - Sparing of face and hands
   - Calf pseudohypertrophy
   - Cardiomyopathy