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Charcot-Marie-Tooth Disease

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Charcot-Marie-Tooth Disease Facts About Charcot-Marie- Tooth Disease & Related Diseases Updated December 2009 Dear Friends: to teach — is that people with disabilities ’ve lived with Charcot-Marie-Tooth are — like everyone else — full of pos- disease (CMT) since my early 20s — I sibilities and gifts. These, not our limita- more than half my life. The disease has tions, are what matter. progressed slowly over the years, mostly affecting my lower legs and hands, so that Another important extended family in my now I use a manual wheelchair part time. life is the Muscular Dystrophy Association, In those years, I’ve continued a career which offers a great program of services, in computer technology, started a small leads the world in CMT research and business, pursued my interests in art and keeps us well informed about the disease. photography, married, and contributed my See “MDA is Here to Help You,” on page knowledge and experience to others with 12, for details of the Association’s pro- disabilities. gram. This booklet has been prepared to give While MDA’s research program continues you the basic knowledge about CMT and making strides toward better treatments Dejerine-Sottas disease (DS) that you’ll and a cure, it’s good to know that people need in order to help you prepare for with disabilities have more opportuni- changes that may occur in your future. ties than ever before to develop and use You’ll learn that CMT is usually quite slow their abilities, and that the laws entitle us in progression and that, while it presents to equal employment opportunities and challenges in daily life, there are many access to public places. techniques and devices to help you adapt to those challenges. As you face the challenges ahead, remem- ber, MDA and all its resources are there You’ll read that many different genetic to help you and your family. You’re not causes of CMT have been found, and alone. cases vary greatly. But CMT is almost never life-threatening, and it seldom George J. Donahue affects the heart and breathing functions. Watertown, Massachusetts And it doesn’t affect intelligence or the spirit. I know of many productive, suc- cessful people with CMT — doctors and scientists, artists and singers, athletes and teachers, active teens and students. I know children with CMT who have bright futures. We’ve all learned to strike a bal- ance between adapting to our limitations and surroundings, and living a fulfilling life despite them. I have the wonderful support of my family and great friends. I’m involved in volun- teer projects that help young people with disabilities, advising them on indepen- dence and entrepreneurship, and raising public awareness about disability wherever I go. What I’ve learned — and what I try 2 CMT • ©2009 MDA What is Charcot-Marie-Tooth Disease? harcot-Marie-Tooth disease (CMT) Because of these features, CMT is Cis a neurological disorder, named sometimes called hereditary motor and after the three physicians who first sensory neuropathy (HMSN). Some described it in 1886 — Jean-Martin doctors also use the old-fashioned Charcot and Pierre Marie of France, name peroneal muscular atrophy, and Howard Henry Tooth of the United which refers to wasting of the peroneal Kingdom. Although most people have muscle in the lower leg. never heard of CMT, it affects some 115,000 Americans. There are even more names for CMT because the disease exists in many dif- Unlike other neurological disorders, ferent forms, each unique in its sever- Brain CMT usually isn’t life-threatening, and it ity, age of onset, progression and exact almost never affects the brain. It causes symptoms. For example, Dejerine- Spinal cord damage to the peripheral nerves — Sottas disease (DS) is a severe form of tracts of nerve cell fibers that connect CMT that manifests during infancy or the brain and spinal cord to muscles early childhood. and sensory organs. Although there’s no cure for CMT, Peripheral nerves control movement by there are treatments that can be used Arm relaying impulses from the spinal cord to to effectively manage its symptoms. muscle muscles. They convey sensation by car- Those treatments, described here along rying feelings like pain and temperature with a general overview of CMT, have from the hands and feet to the spinal allowed many people with the disease cord. They also help control balance, by to lead active, productive lives. carrying information about the position of the body in space. They transmit infor- What causes CMT? mation about the feet and hands to the CMT is caused by defects in genes, Hand spinal cord and then the brain, so that the muscle which are segments of DNA contained Peripheral brain knows where to place the feet when nerves in the chromosomes of the body’s walking and where the hands should be cells. Genes are recipes for making placed to reach for something. Leg (peroneus) the proteins that serve essential func- muscle Nerve damage, or neuropathy, causes tions in our bodies. Each form of CMT muscle weakness and wasting, and is linked to a specific gene, and all of Foot some loss of sensation, mostly in the those genes make proteins found within muscle extremities of the body: the feet, the the peripheral nerves. lower legs, the hands and the forearms. Peripheral nerves provide an essential CMT causes degeneration of the peripheral Although CMT can look very similar relay between your brain and the rest of nerves, leading to muscle weakness in the body’s extremities. to an acquired neuropathy — a type your body. When you decide to move of nerve damage caused by diabetes, your leg, your brain sends an electrical immunological abnormalities or expo- signal to muscle-controlling nerve cells sure to certain chemicals or drugs — it in your spinal cord, which then use the isn’t caused by anything a person does, peripheral nerves to pass the signal on and it isn’t contagious. It’s hereditary, to your leg muscles. meaning that it can be passed down And if you hurt your leg, you feel it through a family from one generation because pain-sensitive nerve cells there to the next. (See “Does it Run in the Family?” page 10.) 3 CMT • ©2009 MDA have sent a signal through your periph- Nerves other than those that go to and eral nerves to your brain. from the extremities can be affected at the severe end of the CMT spectrum. If The peripheral nerves are made up of the nerves that go to and from the dia- fibers, or axons, that extend from sen- phragm or intercostal (between the ribs) sory nerve cells and muscle-controlling muscles are affected, respiratory impair- nerve cells, and carry electrical signals ment can result. to and from the spinal cord. In order for you to move and react with What happens to someone precision and speed, axons have to with CMT, and how is it transmit their signals within a fraction treated? Nerve cell of a second. This is a real challenge for axons that have to stretch over long Partly because there are different types distances, like the ones connected to of CMT, the exact symptoms vary greatly Schwann muscles in your fingers and toes. from person to person. This section pro- cell/Myelin vides a general picture of CMT, and the Axon To give axons a performance boost, each next section describes different types of one is surrounded by a coating called the disease. myelin. Similar to the way plastic coat- Muscle fiber ing is used to insulate electrical wiring, Muscle weakness myelin insulates the electrical signals in In general, people with CMT experience axons. It also provides essential nourish- slowly progressive weakness and wast- ment to the axons. ing in the distal muscles, which control the extremities. These muscles control Some 20 genes have been implicated foot and hand movements. More proxi- in CMT, each one linked to a specific mal muscles, those closer to the trunk, type (and in many cases, more than one such as the leg and arm muscles, are type) of the disease. (See “What are the rarely affected. different types of CMT?” page 7.) Some of those genes make proteins needed Usually, weakness begins in the feet in axons, and others make proteins and ankles, and manifests itself as foot drop — difficulty lifting the foot at the Peripheral nerves control movement by needed in myelin. relaying impulses from the spinal cord (not ankle, so that the toes point downward shown) to the muscles (shown in the fore- Defective myelin genes can cause a during walking. Foot drop causes arm). They also convey sensation and help breakdown of myelin (called demyelin- frequent tripping, and with increasing with balance and awareness of the body’s ation) while defective axon genes can position. weakness and attempts at compensa- cause an impairment of axon function tion, the affected person develops an A single movement-controlling peripheral (axonopathy). abnormal gait. nerve is composed of many long nerve cell branches — or axons — that extend from the spinal cord and connect to muscle In either case, the end result is the Many people with CMT make their first fibers. Each axon is surrounded by myelin same: Defects in the axon or the visits to a neurologist after they notice made from the wrappings of Schwann myelin cause progressive damage to frequent trips and falls, ankle sprains, cells. the axons. or ankle fractures, caused by foot drop. The longest axons in the body are When these problems occur, some especially sensitive to damage, which people find they can overcome them explains why CMT mostly causes motor just by wearing boots or high-top and sensory problems in the body’s shoes to support the ankles.
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