Hereditary sensory motor neuropathy (HSMN)

Question 1

Hereditary sensory motor neuropathy (HSMN) presentation

Answer 1

This man complains of progressive weakness and a change in the appearance of his legs. Please examine him neurologically.

Question 2

Clinical signs of (HSMN)

Answer 2

1. Wasting of distal lower limb muscles with preservation of the thigh muscle bulk (inverted champagne bottle appearance)
2. Pes cavus (seen also in Friedreich’s ataxia)
3. Weakness of ankle dorsi‐flexion and toe extension
4. Variable degree of stocking distribution sensory loss (usually mild)
5. Gait is high stepping (due to foot drop) and stamping (absent proprioception)
6. Palpable lateral popliteal nerve
7. Wasting of hand muscles

Question 3

Discussion of HSMN

Answer 3

1. The commonest HSMN types are I (demyelinating) and II (axonal).
2. Autosomal dominant inheritance (test for PMP22 mutations in HSMN I).
3. HSMN is also known as Charcot–Marie–Tooth disease and peroneal muscular atrophy.

Question 4

Other causes of peripheral neuropathy
Predominantly sensory

Answer 4

1. Diabetes mellitus
2. Alcohol
3. Drugs, e.g. isoniazid and vincristine
4. Vitamin deficiency, e.g. B12 and B1

Question 5

Other causes of peripheral neuropathy
Predominantly motor

Answer 5

1. Guillain–Barré and botulism present acutely
2. Lead toxicity
3. Porphyria
4. HSMN

Question 6

Other causes of peripheral neuropathy
Mononeuritis multiplex

Answer 6

1. Diabetes mellitus
2. Connective tissue disease, e.g. SLE and rheumatoid arthritis
3. Vasculitis, e.g. polyarteritis nodosa and Churg –Strauss
4. Infection, e.g. HIV
5. Malignancy