Duchenne Muscular Dystrophy
Duchenne Muscular Dystrophy (DMD) is a genetic, degenerative muscular disease caused by a recessive defect on the X chromosome. This genetic defect prevents the body from producing dystrophin, a protein which protects the muscle fiber membrane and is required to maintain muscle strength. As a result, patients experience generalized muscle weakness and muscle wasting that eventually affects the heart and respiratory muscles. Patients with DMD, which strikes approximately one in every 3,500 boys, rarely survive beyond their early 30s.
While there is no known cure for DMD, several therapies have demonstrated varying abilities to ease or slow the progression of the disease's symptoms. The Avicena Group is presently developing a novel drug candidate for the treatment of DMD. In initial pilot testing, this compound has shown promising therapeutic results such as increased hand strength.
What is DMD
DMD is a genetic, degenerative muscular disease caused by a defective recessive gene on the X chromosome. As a result of the genetic defect, the body fails to produce the protein dystrophin, which supports the muscle fiber membrane. Dystrophin is one of a number of critical proteins that surround the muscle fiber membrane and keep muscles functioning properly. In the absence of dystrophin, muscle strength in the arms, legs and trunk progressively degenerates. Eventually the heart and respiratory muscles are affected. Patients rarely live beyond their early 30s.
DMD is linked to the X chromosome and is inherited from mother to child. While only boys are affected, girls who carry the defective gene may develop a mild version of the disease.
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Types of DMD
While DMD is not classified into categories, the disease is one of nine types of muscular dystrophy, a group of genetic, degenerative diseases that primarily affect voluntary muscles.
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Symptoms of DMD
The most common symptoms of DMD are a generalized weakness and muscle wasting that first affects the hips, pelvic area, thighs and shoulders. Children with DMD typically begin to show signs of muscle weakness as early as age two. The disease gradually weakens the skeletal or voluntary muscle groups in the arms, legs and trunk. Initially, these weaknesses lead to difficulty in standing up, climbing stairs and maintaining balance. Later in life, these symptoms expand to include weakening and wasting of heart and respiratory muscles.
Additionally, approximately one-third of boys with DMD have some degree of learning disability, although few suffer from serious mental retardation.
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Progression of DMD
The progression of DMD follows a well-known pattern. Children with the disorder typically take longer to learn to walk. Toddlers usually have enlarged calf muscles, while pre-schoolers may appear clumsy. Eventually, a child with DMD will have trouble running, climbing stairs or getting up from the floor.
At school age, a child with DMD may walk on his toes or the balls of his feet. Children will exhibit an unsteady gait and can fall easily. As the disease progresses, the child will have difficulty raising his arms. At this stage, children may also develop learning disabilities including a reduced attention span, impaired memory, and reduced emotional interaction.
Nearly all children afflicted with DMD lose the ability to walk between ages of 7 and 12. In subsequent years, movement involving the arms, legs or trunk may require assistance or mechanical support.
At approximately 10 years of age, the diaphragm and other muscles that operate the lungs may weaken, leading to a compromised respiratory system and an increased risk of infections.
By the teen years, the heart and respiratory muscles may have weakened to the point at which the disease becomes life threatening. Patients with DMD rarely survive beyond their early 30s.
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Diagnosis of DMD
Diagnosis of DMD typically begins with a physical examination and a detailed analysis of family history regarding the disease. Genetic testing is typically relied on in order to confirm a diagnosis of DMD.
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Causes of DMD
DMD is a genetic, degenerative muscular disease that is caused by a defective recessive gene inherited from mother to child. This genetic defect prevents the body from producing dystrophin, a protein which protects the muscle fiber membrane and is required to maintain muscle strength.
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Incidences of DMD
DMD usually strikes between the age of 3 and 6, and only affects boys. Crossing all race and ethnic groups, DMD affects approximately 1 in every 3,500 boys.
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Treatment of DMD
While there is no known cure for DMD, certain medications or treatments have been shown to ease the symptoms associated with the disease. To postpone or minimize symptoms, a physician may prescribe physical therapy such as "range of motion" exercises or certain drugs such as catabolic steroids. Furthermore, physicians may prescribe braces or walkers to aid in daily life. Ultimately, DMD patients become reliant on wheelchairs for mobility.
The Avicena Group is presently developing a novel drug candidate for the treatment of DMD. In initial pilot testing by Dr. Mark Tarnopolsky at McMaster University, this compound has shown promising therapeutic results such as increased hand strength.
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