Rare Disease Report

September is Charcot-Marie-Tooth (CMT) Disease Awareness Month

SEPTEMBER 14, 2016
James Radke, PhD
September is Charcot-Marie-Tooth (CMT) Disease Awareness Month. Lead CMT advocacy group, the Hereditary Neuropathy Foundation will be promoting numerous events this month to help raise awareness of CMT, including:

HNF is also a strategic alliance partner with Rare Disease Report so look for updates on that page this month as well as our coverage of their patient conference in October (www.raredr.com/sap-partner/hereditary-neuropathy-foundation

Types of CMT 

There are many forms of CMT disease, including CMT1, CMT2, CMT3, CMT4, and CMTX. 

CMT1, caused by abnormalities in the myelin sheath, has several subgroups. CMT1A is an autosomal dominant disease that results from a duplication of the gene on chromosome 17 that carries the instructions for producing the peripheral myelin protein-22 (PMP-22). This is the most common type of CMT found and affects approximately 125,000 people in the United States and Europe. CMT1B is an autosomal dominant disease caused by mutations in the gene that carries the instructions for manufacturing the myelin protein zero (P0). The less common CMT1C, CMT1D, and CMT1E are caused by mutations in the LITAF, EGR2, and NEFL genes, respectively.

CMT2 results from abnormalities in the axon of the peripheral nerve cell rather than the myelin sheath. It also has subgroups based on the genes associated with them (CMT2A, CMT2B, CMT2D, CMT2E, CMT2H, and CMT2.

CMT3 or Dejerine-Sottas disease is a severe demyelinating neuropathy that begins in infancy. It is caused by a specific point mutation in the P0 gene or a point mutation in the PMP-22 gene.

CMT4 comprises several different subtypes of autosomal recessive demyelinating motor and sensory neuropathies. It also has subgroups based on the genes associated with them CMT4A, CMT4B1, CMT4B2, CMT4C, CMT4D, CMT4E, CMT4F, CMT4H, CMT4J.

CMTX is caused by a point mutation in the connexin-32 gene on the X chromosome. Males who inherit one mutated gene from their mothers show moderate to severe symptoms of the disease beginning in late childhood or adolescence. Females may develop mild symptoms in adolescence or later or may not develop symptoms of the disease at all.

Symptoms of CMT

Symptoms vary depending on the type of CMT but common early symptoms may include
  • Clumsiness
  • slight difficulty in walking because of trouble picking up the feet
  • weak leg muscles
  • fatigue

Other common symptoms of CMT as it progresses include
  • foot deformity (very high arched foot/feet)
  • difficulty lifting foot at the ankle (foot drop)
  • curled toes (known as hammer toes)
  • loss of lower leg muscle, which leads to skinny calves
  • numbness or burning sensation in the feet or hands
  • “slapping” when walking (feet hit the floor hard when walking)
  • weakness of the hips, legs, or feet
  • leg and hand cramps
  • loss of balance, tripping, and falling
  • difficulty grasping and holding objects and opening jars and bottles

Treatment of CMT

Currently, there are no treatments available for CMT other than supportive care (orthotics, leg braces, surgery, physical therapy) but French company Pharnext is currently conducting a Phase 3 clinical trial testing the safety and efficacy of PXT3003 in CMT1A patients.

And in October....

On October 6, HNF will be hosting the first PatientCentered Charcot-Tooth-Marie Summit in New York City. The summit will connect patients with leader in industry, research, and treatment.  To register, click here.

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