Charcot-Marie-Tooth disease type 1A (CMT1A) is a common inherited neurological disorder affecting the peripheral nerves. These nerves transmit signals between the central nervous system and the rest of the body. In CMT1A, this communication pathway is disrupted, impairing the body’s ability to send and receive information effectively.
Understanding CMT1A
CMT1A is a genetic condition stemming from a specific alteration on chromosome 17. This alteration involves a duplication of the PMP22 gene. The PMP22 gene provides instructions for making a protein that is a component of myelin. Myelin forms a protective covering around nerve fibers, similar to insulation around an electrical wire, allowing for rapid and efficient transmission of nerve signals.
The duplication of the PMP22 gene leads to an overproduction of the PMP22 protein. This excess protein disrupts the normal formation and maintenance of the myelin sheath, causing it to degrade. As a result, the peripheral nerves, including both motor and sensory nerves, cannot conduct signals properly. This impaired nerve function underlies the physical challenges experienced by individuals with CMT1A.
Recognizing the Signs
Symptoms of CMT1A often begin during childhood or adolescence, though the age of onset varies. Muscle weakness typically appears first in the feet and lower legs, leading to difficulties with walking and balance. This weakness can cause foot drop, where an individual struggles to lift the front part of their foot, leading to a high-stepping gait. Foot deformities are also common, including high arches (pes cavus) or hammer toes.
As the condition progresses, muscle weakness can extend to the hands, making fine motor tasks challenging. Activities such as buttoning clothes, writing, or opening jars may become increasingly difficult. Individuals may also experience sensory loss, characterized by numbness, tingling, or reduced sensation, particularly in the feet and hands. These sensory changes can increase the risk of unnoticed injuries. Symptoms generally worsen over time, though the rate of progression varies.
Diagnosing CMT1A
Diagnosing CMT1A begins with a thorough medical history and physical examination. A doctor will look for characteristic signs such as muscle weakness in the lower legs and hands, diminished reflexes, and foot deformities like high arches. They will also assess sensory function to identify any areas of numbness or reduced sensation. These initial observations help guide further diagnostic steps.
Nerve conduction studies (NCS) and electromyography (EMG) are performed to evaluate nerve function. NCS measures how quickly electrical signals travel through nerves, revealing slowed conduction velocities due to myelin damage. EMG assesses the electrical activity of muscles, helping to determine if muscle weakness is due to a nerve problem. The definitive diagnosis of CMT1A is confirmed through genetic testing, which confirms the duplication of the PMP22 gene. This genetic confirmation is important for accurate diagnosis and family planning.
Managing CMT1A
While there is currently no cure for CMT1A, various management strategies focus on alleviating symptoms and improving quality of life. Physical therapy is a primary management strategy, helping individuals maintain muscle strength, improve flexibility, and enhance balance. Therapists guide exercises designed to strengthen weakened muscles and stretch tight ones, which can help prevent contractures and maintain mobility. Regular engagement in these exercises can also help mitigate the progressive nature of muscle weakness.
Occupational therapy assists individuals in adapting to daily tasks and maintaining independence. This may involve recommending adaptive equipment or modifying activities to make them easier to perform, such as using specialized utensils or assistive devices for dressing. Orthotic devices, particularly ankle-foot orthoses (AFOs), are often prescribed to support the feet and ankles, helping to manage foot drop and improve gait stability. These braces can enhance mobility and reduce the risk of falls.
Surgical interventions may also be considered to correct severe foot deformities or address joint instability that impacts walking. Pain management strategies address any nerve pain or muscle cramps that may arise.
Living with CMT1A
Living with CMT1A involves a comprehensive approach to care that includes a multidisciplinary team. Neurologists oversee medical management, while physical and occupational therapists provide ongoing support for movement and daily activities. Genetic counselors offer guidance regarding the inherited nature of CMT1A and family planning. This collaborative approach helps ensure all aspects of the condition are addressed.
Lifestyle adjustments also play a role in managing CMT1A. Choosing appropriate footwear that provides good support and accommodates foot deformities is important for comfort and stability. Modifying certain activities or finding alternative ways to perform tasks can help prevent injury and conserve energy. Connecting with support groups and community resources provides individuals and families with valuable emotional support, shared experiences, and practical advice. Understanding the condition and proactively managing its effects can enable individuals to live fulfilling lives.
References
Charcot-Marie-Tooth Disease Fact Sheet. National Institute of Neurological Disorders and Stroke. Accessed July 29, 2025.