Muscular dystrophy (MD) is a group of muscle diseases that result in increasing weakening and breakdown of skeletal muscles over time. The disorders differ in which muscles are primarily affected, the degree of weakness, how fast they worsen, and when symptoms begin (NINDS Muscular Dystrophy Information Page. NINDS. March 4, 2016. Archived from the original on 30 July 2016. Retrieved 12 September 2016). Many people will eventually become unable to walk and some types are also associated with problems in other organs (Muscular Dystrophy: “Hope Through Research”. NINDS. March 4, 2016. Archived from the original on 30 September 2016. Retrieved 12 September 2016).
There are seven major forms of muscular dystrophy:
Myotonic (also called MMD or Steiner’s disease)
The most common form of muscular dystrophy in adults, myotonic muscular dystrophy, affects both men and women, and it usually appears any time from early childhood to adulthood. In rare cases, it appears in newborns (congenital MMD). The name refers to a symptom, myotonic — prolonged spasm or stiffening of muscles after use. This symptom is usually worse in cold temperatures. The disease causes muscle weakness and also affects the central nervous system, heart, gastrointestinal tract, eyes, and hormone-producing glands. In most cases, daily living isn’t restricted for many years and those with myotonic MD have a decreased life expectancy.
The most common form of muscular dystrophy in children, duchenne muscular dystrophy affects only males and it appears between the ages of 2 and 6. The muscles decrease in size and grow weaker over time yet may appear larger. Disease progression varies, but many people with Duchenne (1 in 3,500 boys) need a wheelchair by the age of 12. In most cases, the arms, legs, and spine become progressively deformed, and there may be some cognitive impairment. Severe breathing and heart problems mark the later stages of the disease. Those with Duchenne MD usually die in their late teens or early 20s.
This form is similar to Duchenne muscular dystrophy, but the disease is much milder: symptoms appear later and progress more slowly. It usually appears between the ages of 2 and 16 but can appear as late as age 25. Becker muscular dystrophy affects only males (1 in 30,000) and causes heart problems. Disease severity varies and those with Becker can usually walk into their 30s and live further into adulthood.
This appears in the teens to early adulthood and affects males and females. In its most common form, Limb-girdle muscular dystrophy causes progressive weakness that begins in the hips and moves to the shoulders, arms, and legs. Within 20 years, walking becomes difficult or impossible and sufferers typically live to middle age to late adulthood.
Facioscapulohumeral refers to the muscles that move the face, shoulder blade, and upper arm bone. This form of muscular dystrophy appears in the teens to early adulthood and affects males and females. It progresses slowly, with short periods of rapid muscle deterioration and weakness. Severity ranges from very mild to completely disabling – Walking, chewing, swallowing, and speaking problems can occur. About 50% of those with facioscapulohumeral MD can walk throughout their lives, and most live a normal life span.
Oculopharyngeal means eye and throat. This form of muscular dystrophy appears in men and women in their 40s, 50s, and 60s. It progresses slowly, causing weakness in the eye and face muscles, which may lead to difficulty swallowing
This group of rare diseases affects adult men and women. It causes weakness and wasting of the distal muscles (those farthest from the centre) of the forearms, hands, lower legs, and feet. It is generally less severe, progresses more slowly, and affects fewer muscles than other forms of muscular dystrophy.
The prognosis for people with MD 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 MD die in infancy while others live into adulthood with only moderate disability (National Institute of Neurological Disorders and Stroke: Factsheet).