Charcot-Marie-Tooth Neuropathy Type 1 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY

NOTE: THIS PUBLICATION HAS BEEN RETIRED. THIS ARCHIVAL VERSION IS FOR HISTORICAL REFERENCE ONLY, AND THE INFORMATION MAY BE OUT OF DATE.

Clinical characteristics: Charcot-Marie-Tooth neuropathy type 1 (CMT1) is a demyelinating peripheral neuropathy characterized by distal muscle weakness and atrophy, sensory loss, and slow nerve conduction velocity. It is usually slowly progressive and often associated with pes cavus foot deformity and bilateral foot drop. Affected individuals usually become symptomatic between age five and 25 years. Fewer than 5% of individuals become wheelchair dependent. Life span is not shortened.

Diagnosis/testing: CMT1A (70%-80% of all CMT1) involves duplication of PMP22. CMT1B (6%-10% of all CMT1) is associated with single-nucleotide variants in MPZ. CMT1C (1%-2% of all CMT1) is associated with pathogenic variants in LITAF, and CMT1D (<2% of all CMT1) is associated with pathogenic variants in EGR2. CMT1E (<5% of all CMT1) is associated with single-nucleotide variants in PMP22. CMT2E/1F (<5% of all CMT1) is associated with pathogenic variants in NEFL.

Management: Treatment of manifestations: Treatment by a multidisciplinary team including a neurologist, physiatrist, orthopedic surgeon, physical and occupational therapists; special shoes and/or ankle/foot orthoses to correct foot drop and aid walking; surgery as needed for severe pes cavus; forearm crutches, canes, wheelchairs as needed for mobility; exercise as tolerated.

Prevention of secondary complications: Daily heel cord stretching to prevent Achilles' tendon shortening.

Surveillance: Regular foot examination for pressure sores.

Agents/circumstances to avoid: Obesity (makes ambulation more difficult); medications (e.g., vincristine, isoniazid, nitrofurantoin) known to cause nerve damage.

Pregnancy management: Affected pregnant women may experience worsening symptoms during or after gestation; a higher occurrence of presentation anomalies, use of forceps, and operative delivery; and/or an increased incidence of post-partum bleeding.

Genetic counseling: CMT1 is inherited in an autosomal dominant manner. About two thirds of probands with CMT1A have inherited the PMP22 duplication; about one third have CMT1A as the result of a de novo pathogenic variant. Similar data are not available for the other subtypes of CMT1. The offspring of an individual with any of the subtypes of CMT1 have a 50% chance of inheriting the altered gene. Prenatal testing is possible if the pathogenic variant has been identified in the family. Requests for prenatal testing for typically adult-onset diseases that do not affect intellect or life span are uncommon.