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 |