Charcot Marie Tooth Disease
Classification
Type 1, 2, 3 – most common
Type 1 HMSN: demyelinating
Type 1A: HMSN – demyelinating CMT
- most common
- AD
- genetic duplication on chromosome 17
- motor nerve conduction velocity is delayed
- nerve biopsies
- segmental demyelination
- hypertrophic changes with “onion bulb” formation
Type 1B: HMSN
- AR
- similar to type 1A, but appears more severe with earlier onset
- Roussy-Lévy disease
- variant of HSMN
- Similar to HMSN 1 with associated tremor or ataxia
- There is X-Linked dominant form, which primarily affects males, though females may be symptomatic, clinically similar to HSMN – 1
Type II HMSN: axonal
- neuronal or axonal CMT
- age of onset is generally later, though distribultion & severity of muscle weakness are similar
- AD, & AR
- Motor nerve conduction velocity may be normal or only slightly reduced
- Nerve biopsy
- axonal degeneration
Type III HMSN: hypertrophic polyneuropathy
- Déjèrine – Sopttas disease
- AD
- Starts in infancy
- Children
- absent reflexes
- walk late
- wheelchair bound in second decade of life
- Marked sensory loss in all four extremities
- skeletal deformity, particularly scoliosis
- Ataxia is universal
- Nerve biopsy
- hypomyelination
- demyelination
Type IV HMSN: Refsum’s disease
- Hypertrophic neuropathy
- AR disorder
- Starts
- childhood, or at puberty
- ↑ phytanic acid in serum
- Associations
- Atypical pigmentary degeneration of retina
- cerebellar limb ataxia
- cardiomyopathy
- sensorineural deafness
- distal sensory & motor loss in the hands & feet
Type V:
- inherited spastic paraplegia with distal weakness in limbs
- usually presents in second decade of life or later
- patients develop awkward gait & equinus foot deformities
- type VI involves optic atrophy in association with peroneal muscular atrophy
- type VII is characterized by retinitis pigmentosa associated with distal muscle weakness in limbs & atrophy