Pathophysiology
1) heterogeneous group of hereditary peripheral neuropathies 2) type 1 – most common; marked by demyelination 3) type 2 – less severe clinically; lacks demyelination 4) type 3 (Dejerine-Sottas disease) – infantile onset; severe symptoms 5) type 4 – rare; X-linked recessive 6) frequency for all variants combined is 1/2,500
Signs and Symptoms
1) onset is in adolescence with both motor and sensory deficits 2) distal extremity weakness 3) distal atrophy 4) decreased deep tendon reflexes 5) high stepping gait 6) frequent falls 7) abnormal feet (commonly pes cavus or high arches)
Characteristic Test Findings
EMG – 1) type 1 – decreased nerve-conduction velocity 2) type 2 – normal or only slightly decreased nerve-conduction velocity
Histology/Gross Pathology
1) type 1 – axonal degeneration, segmental demyelination, onion bulbs, and nerve hypertrophy 2) type 2 – distal axonal degeneration only
Associated Conditions
1) focal segmental glomerulosclerosis 2) destructive arthritis
Inheritance/Epidemiology
1) autosomal dominant 2) most common peripheral hereditary neuropathy 3) type 1A – gene deficit is duplication-type defect on chromosome 17 (likely involves peripheral myelin protein 22) 4) type 1B – gene defect on chromosome 1 (likely involves myelin protein zero) 5) type 1A most common variant
Tips for USMLE
all drugs with known neurologic side effects should be avoided (e.g., vincristine, metronidazole)
My daughter is 10 she has CMT type, My daughter comes from a family of CMT suffers who are significantly effected , 2 members of the family have suffered leg amputations she has significant muscle wastage , mobility difficulties , significant and rapid progression , ankle and foot problems /calluses,ankle weakness, bone deformity , she has hip problems and scoliosis , she will need a number of operations she uses a number of aids to assist her with day to day tasks .
My Daughter uses leg braces , wheelchair , special trike because she cant ride standard bike , We do regular physio,low impact exercise/stretching and it helps massively , so do treatments like massage , heat therapy , exercise equipment following a daily physio and exercise program is hard but has worked for us , other therapies explored , plenty of swimming and expert bracing and orthotics ,the benefits of modern bracing techniques and materials must be explored, We have had amazing results bracing is prolonging the need for major surgery
We have many medical appointments with a complex team of therapists , we have lost count of the many many times we have had to educate therapists who have never heard of CMT let alone treated CMT , Schools need a better understanding of how children can be effected
We run support and contact groups for people living with CMT , Awareness is extremely important to us please visit The Georgia Allen Fund For Charcot Marie Tooth http://www.thegeorgiaallenfund.com for latest news and events