Health Dictionary
Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.
Charcot-Marie-Tooth disease classification
Introduction
Overview
Overview
Classification
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
References
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]