Charcot-Marie-Tooth Flashcards
CMT is also known as..?
Hereditary Motor and Sensory Neuropathy
Number of genes for CMT?
35
Prevalence?
1/3300
Categorization of CMT?
CMT1- disorders causing demyelination
CMT2- disorders causing axonal problems
Major feature of CMT?
Impaired motor and sensory nerve function e.g. foot drop, loss of sensation in hands/feet, weakness in hands (later than feet)
Inheritance pattern and causative mutation of CMT1A?
Autosomal dominant; 1.5MB genomic duplication of 17p11.2 - 17p12, region containing PMP22 gene- commonest cause of CMT
(rarely results from PMP22 point mutations)
Other phenotype caused by deletion of 17p11.2 - 17p12?
Hereditary neuropathy with liability to pressure sores
Main features of CMT1A?
Abnormal myelin with slow nerve conduction causing distal muscle weakness, sensory loss, may become wheelchair dependent later in life
Causative mutation: CMT1B
MPZ
Causative mutation: CMT1C
LITAF
How does CMT2 differ from CMT1?
Axonopathy, nerve conduction is usually normal. Similar problems to CMT1 but less disabled
Rare combination of myelinopathy and axonopathy
CMT3 (aka intermediate form)
Rare autosomal recessive form of CMT which can be either myelinopathy or axonopathy
CMT4
How can X-linked CMT and dominant CMT be distinguished?
Absence of male-male transmission
Features of X-linked CMT?
Axonopathy with secondary myelin changes
Deafness and CNS symptoms
Mild to no symptoms in carrier females
