Charcot-Marie-Tooth Neuropathy Type 4 – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY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 THIS ARCHIVAL VERSION IS FOR HISTORICAL REFERENCE ONLY, AND THE INFORMATION MAY BE OUT OF DATE.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 4 (CMT4) is a group of progressive motor and sensory axonal and demyelinating neuropathies that are distinguished from other forms of CMT by autosomal recessive inheritance. Affected individuals have the typical CMT phenotype of distal muscle weakness and atrophy associated with sensory loss and, frequently, pes cavus foot deformity.

Diagnosis/testing: The diagnosis of CMT4 subtypes is based on clinical findings, neurophysiologic studies, and molecular genetic testing. Detection of biallelic pathogenic variants in one of the following 11 genes establishes the diagnosis: GDAP1 (CMT4A), MTMR2 (CMT4B1), SBF2 (CMT4B2), SBF1 (CMT4B3), SH3TC2 (CMT4C), NDRG1 (CMT4D), EGR2 (CMT4E), PRX (CMT4F), HK1 (CMT4G), FGD4 (CMT4H), and FIG4 (CMT4J).

Management: Treatment of manifestations: Treatment by a 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; symptomatic treatment of pain, depression, sleep apnea, restless leg syndrome.

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

Surveillance: Monitoring gait and condition of feet to determine need for bracing, special shoes, surgery.

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

Other: Career and employment counseling.

Genetic counseling: The CMT4 subtypes are inherited in an autosomal recessive manner. Parents of an affected individual are obligate carriers of the CMT4-related pathogenic variant present in their family. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if the pathogenic variants in an affected family member are known.