Definition: Defining the Meaning of Muscular Dystrophy
Muscular dystrophy (MD) is a group of muscle diseases that weaken the musculoskeletal system and hamper locomotion. Muscular dystrophies are characterized by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cells and tissue. There is no known cure for muscular dystrophy, although significant headway is being made with antisense oligonucleotides.
What is Muscular Dystrophy
Muscular dystrophy refers to a group of genetic, hereditary muscle diseases that cause progressive muscle weakness.
Muscular dystrophies are characterized by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cells and tissue.
Nine diseases including Duchenne, Becker, limb girdle, congenital, facioscapulohumeral, myotonic, oculopharyngeal, distal, and Emery-Dreifuss are always classified as muscular dystrophy but there are more than 100 diseases in total with similarities to muscular dystrophy.
Most types of MD are multi-system disorders with manifestations in body systems including the heart, gastrointestinal and nervous systems, endocrine glands, skin, eyes and other organs.
The best-known type, Duchenne muscular dystrophy (DMD), is inherited in an X-linked recessive pattern, meaning that the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes, and is thus considered sex-linked. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition.
In females (who have two X chromosomes), a mutation must generally be present in both copies of the gene to cause the disorder (relatively rare exceptions, manifesting carriers, do occur due to dosage compensation/X-inactivation).
Males are therefore affected by X-linked recessive disorders much more often than females.
A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons. In about two thirds of DMD cases, an affected male inherits the mutation from a mother who carries one altered copy of the DMD gene. The other one third of cases probably result from new mutations in the gene. Females who carry one copy of a DMD mutation may have some signs and symptoms related to the condition (such as muscle weakness and cramping), but these are typically milder than the signs and symptoms seen in affected males. Duchenne muscular dystrophy and Becker's muscular dystrophy are caused by mutations of the gene for the dystrophin protein and lead to an overabundance of the enzyme creatine kinase. The dystrophin gene is the largest gene in humans.
Types of Muscular dystrophy:
- Becker's muscular dystrophy
- Congenital muscular dystrophy
- Duchenne muscular dystrophy
- Distal muscular dystrophy
- Emery-Dreifuss muscular dystrophy
- Limb-girdle muscular dystrophy
- Myotonic muscular dystrophy
- Oculopharyngeal muscular dystrophy
Symptoms of Muscular dystrophy include:
- Progressive Muscular Wasting (weakness)
- Poor Balance
- Frequent Falls
- Walking Difficulty
- Waddling Gait
- Calf Pain
- Limited Range of Movement
- Muscle Contractions
- Respiratory Difficulty
- Drooping Eyelids (ptosis)
- Gonadal Atrophy
- Scoliosis (curvature of the spine)
- Inability to walk
- Some types of Muscular Dystrophy can affect the heart, causing cardiomyopathy or arrhythmias.
The prognosis for people with muscular dystrophy varies according to the type and progression of the disorder. Some cases may be mild and progress very slowly over a normal lifespan, while others produce severe muscle weakness, functional disability, and loss of the ability to walk. Some children with muscular dystrophy die in infancy while others live into adulthood with only moderate disability. The muscles affected vary, but can be around the pelvis, shoulder, face or elsewhere. Muscular dystrophy can affect adults, but the more severe forms tend to occur in early childhood.
There is no known cure for muscular dystrophy. Inactivity (such as bed-rest and even sitting for long periods) can worsen the disease. Physical therapy, Occupational therapy, speech therapy and orthopedic instruments (e.g., wheelchairs, standing frames) may be helpful.
Physical therapy to prevent contractures (a condition when an individual with a muscular dystrophy grows and the muscles don't move with the bones and can easily be slowed down and/or make the individual's body straighter by daily physical therapy), orthoses (orthopedic appliances used for support) and corrective orthopedic surgery may be needed to improve the quality of life in some cases. The cardiac problems that occur with Emery-Dreifuss muscular dystrophy and myotonic muscular dystrophy may require a pacemaker. The myotonia (delayed relaxation of a muscle after a strong contraction) occurring in myotonic muscular dystrophy may be treated with medications such as quinine, phenytoin, or mexiletine but no actual long term treatment has been found.
Muscular Dystrophy Awareness
The awareness ribbon color for muscular dystrophy is lime green. Duchenne muscular dystrophy awareness day is on September 7th. September is Muscular Dystrophy Awareness Month. Duchenne muscular dystrophy is a devastating disease which affects approximately 250.000 children around the world.
Quick Facts: Muscular Dystrophy Prognosis
Prognosis depends on the individual form of muscular dystrophy. In some cases a person with a muscle disease will get progressively weaker to the extent that it shortens life span due to heart and breathing complications. However, some of the muscle diseases do not affect life expectancy at all. There is a tremendous amount of ongoing research to find cures and treatments to slow muscle weakness. There is also a lot of research to learn how best to manage the breathing and heart issues which generally impact lifespan more than the muscle weakness.
Statistics: U.S. Muscular Dystrophy
In 2007, 349 out of 2.37 million males aged 5-24 years were reported to have DMD or BMD in the United States. This means that about 15 out of every 100,000 males ages 5-24 years were affected that year.
Which muscles usually show weakness first
Upper arms, Upper legs
Are males or females more likely to be affected
When does muscle weakness typically begin
DMD: Before 5 years; BMD: Between 7-12 years
What other parts of the body can be affected
Brain, Throat, Heart, Diaphragm/Chest Muscles, Stomach, Intestines, Spine