Charcot-Marie-Tooth disease classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Classification

  • CMT Type 1 (CMT1): Type 1 affects approximately 80% of CMT patients and is the most common type of CMT. The subtypes share clinical symptoms. Autosomal dominant. Causes demyelination, which can be detected by measuring nerve conduction velocities.
  • CMT Type 2 (CMT2): Type 2 affects approximately 20-40% of CMT patients. Type 2 CMT is Autosomal dominant neuropathy with its main effect on the axon. The average nerve conduction velocity is slightly below normal, but generally above 38 m/s
  • CMT Type 3 (CMT3): Type 3 affects a very few CMT patients.
  • CMT Type 4 (CMT4): Type 4 affects a very few CMT patients.
  • CMT X-Linked (CMTX): CMTX affects approximately 10-20% of CMT patients and is X-linked dominant. Approx 10% of X-linked CMT patients have some other form than CMTX.

More details on the types are provided in the table below:

Type OMIM Gene Locus Description
CMT1A 118220 PMP22 17p11.2 The most common form of the disease, 70-80% of Type 1 patients. Average NCV: 15-20 m/s when associated with essential tremor and ataxia, called Roussy-Levy Syndrome
CMT1B 118200 MPZ 1q22 Caused by mutations in the gene producing protein zero (P0). 5-10% of Type 1 patients. Average NCV: <20 m/s
CMT1C LITAF 16p13.1-p12.3 Causes severe demyelination, which can be detected by measuring nerve conduction velocities. Autosomal dominant. Usually shows up in infancy. Average NCV: 26-42 m/s. Identical symptoms to CMT-1A.
CMD1D EGR2 10q21.1-q22.1 Average NCV: 15-20 m/s
CMT2A 118210 MFN2 or KIF1B 1p36 The cause is likely located on chromosome 1 for the mitofusion 2 protein. Some research has also linked this form of CMT to the protein kinesin 1B. Does not show up on nerve conduction velocity tests, because it is caused by axonopathy.
CMT2B 600882 RAB7 (RAB7A, RAB7B) 3q21.
CMT2B1 LMNA 1q22 Autosomal recessive axonal CMT, (laminopathy)
CMT2C 606071 12q23-q24 May cause vocal cord, diaphragm, and distal weaknesses.
CMT2D 601472 GARS 7p15 Patients with mutations in the GARS gene tend to have more severe symptoms in the upper extremities (hands), which is atypical for CMT in general.
CMT2E NEFL 8p21
CMT2F 606595 HSPB1 7q11-q21
CMT2G 608591 12q12-13
CMT2H 607731 GDAP1 8q13-q21.1
CMT2J 607736 1q22
CMT2K 607831 8q13-q21.1
CMT2L 608673 12q24
CMT3 145900 varies varies Sometimes called Dejerine-Sottas disease. Rarely found. Autosomal recessive. Average NCV: Normal (50-60m/s)
CMT4A 214400 GDAP1 8q13-q21.1 Autosomal recessive.
CMT4B1 601382 MTMR2 11q22 Autosomal recessive.
CMT4B2 CMT4B2 (SBF2) 11p15 May be called "SBF2/MTMR13". Autosomal recessive.
CMT4C KIAA1985 (SH3TC2) 5q32 May lead to respiratory compromise.
CMT4D 601455 NDRG1 8q24.3 Autosomal recessive, demyelinating, deafness
CMT1E 118300 PMP22 17p11.2 Autosomal dominant, demyelinating, deafness
CMT4E EGR2 10q21.1-10q22.1 "CMT4E" is a tentative name
CMT4F PRX 19q13.1-19q13.2 "CMT4F" is a tentative name
CMT4J 611228 KIAA0274 (FIG4) 6q21 Autosomal recessive
CMTX1 302800 GJB1 Xq13.1 Average NCV: 25-40 m/s
CMTX2 302801 Xq22.2
CMTX3 302802 Xq26
CMT 118301 with Ptosis and Parkinsonism
CMT 302803 type 1 aplasia cutis congenita


References

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