The muscular dystrophies, or MD, are a group of more than 30 genetic (passed down by parents) neuromuscular disorders, in which defects of muscle (not nerves) cause muscle weakness and difficulties in body movement and control. Each type of muscular dystrophy is passed on by a different gene, and they all have different courses. However, all of the disorders are always progressive (worsen over time), and always involve destruction and death of muscle fibers at some stage of the disease. MD can begin in infancy, childhood, or adulthood. However, those which start in early childhood are most severe.
Symptoms are different, depending on the type of muscular dystrophy. Every muscle in the body may be affected in some types. While, only certain muscles may be affected in others.
Symptoms may include:
There are seven major types of muscular dystrophy that affect children and young adults:
Duchenne muscular dystrophy is the most common inherited neuromuscular disorder that affects all races and ethnicities. Affecting only males, it occurs in 1/3,600 live-born infant boys. While some affected newborns may have some mild hypotonia (decreased muscle tone or “floppiness”), other symptoms are rarely present at birth or in early infancy. Early gross motor developmental milestones, including rolling over, sitting, and standing, are usually met at the normal ages, or slightly later than normal. The first sign of muscle weakness is often poor head control. Many children begin walking at the appropriate age, around 12 months. However, weakness of hip muscles may start as early as the 2nd year of life, causing affected toddlers to stand with their lower back arched forward. Between three and five years of age, affected children become unable to stand up from squatting position without pushing through their arms (Gower’s sign), and begin to walk with a waddle (Trendelenburg gait). Children may lose the ability to walk as early as 7 years of age. Most will become confined to a wheelchair by the age of 10-12 years. Those affected usually maintain the ability to be able to use their hands to hold and use eating and writing utensils. All children with DMD will have some degree of intellectual impairment, with most having only learning disabilities.
Muscle weakness and breakdown continues to progress throughout life, causing development of many complicating disorders and the common signs and symptoms of the disease. Calf muscles commonly become enlarged (psuedohypertrophy), and thigh muscles become thin. The tongue and forearm muscles may also become enlarged. Stiffening of the joints (contractures) may occur. Many children will develop severe spinal curvature (scoliosis), particularly after becoming confined to a wheelchair. Weakness in chest and throat muscles leads to difficulty coughing and swallowing, causing frequent lung infections. Breakdown of the heart muscle (cardiomyopathy) is typical. With a life expectancy of about 18 years of age, heart and respiratory complications are most commonly the cause of death in patients with DMD.
Characteristic features of Duchenne Muscular Dystrophy:
Becker muscular dystrophy is the same basic disease as Duchenne muscular dystrophy, except it is less common and the symptoms are milder and slower to progress. It also only affects males, and occurs in about 1/30,000. Symptoms often begin during adolescence. Once symptoms begin, they follow a slower, but similar, course to that of Duchenne muscular dystrophy. Patients continue to be able to walk through late teens to early adulthood. Enlarged calves (pseudohypertrophy) and the breakdown of heart muscle (cardiomyopathy) are much the same as in those with Duchenne muscular dystrophy. Learning disabilities are less common in Becker MD. Many patients die, due to complications, in their mid-to-late 20s. Less than half of those with Becker MD survive to 40 years of age. Those that do are typically severely disabled.
Myotonic muscular dystrophy, also known as MMD or Steinert’s disease, is the most common form of MD in adults. It occurs in 1/30,000 people. It occurs in males and females, with symptoms typically beginning any time from early childhood through adulthood. One symptom of the disorder is myotonia, a condition in which muscles have trouble relaxing after use (prolonged spasm). The spasms are not painful. Other symptoms may include muscle weakness, slurred speech, difficulties swallowing, constipation, or abnormal heart beat (arrhythmia). MMD may also be associated with low immune system, cataracts, thyroid disorders, or diabetes. Many men with MMD experience infertility and early onset of frontal baldness, while, women with MMD may have difficulties with childbirth due to weak muscles of the uterus. It is unusual for people with this form of MD to lose the ability to walk. However, braces or other assistive devices may become necessary. Although, about 50% of those with myotonic dystrophy have less than average intelligence, severe mental impairment is rare. Others will have average, or occasionally above average, intelligence.
Limb-Girdle muscular dystrophy affects males and females. Most commonly it causes progressive (worsening) hip and shoulder muscle weakness that spreads to the arms, legs, and back. Symptoms usually begin between 8 and 15 years of age, and progress slowly. Initially, patients may experience low back pain as they begin to stand with their lower back arched forward to compensate for weak buttock muscles. Overtime, muscles of the arms and legs begin to shrink (atrophy). Neck muscles become weak, as well. Patients usually become confined to a wheelchair by 30 years of age. Intelligence is usually normal. Heart muscle involvement is uncommon.
Facioscapulohumeral muscular dystrophy is also known as Landouzy-Dejerine. Affecting both males and females, symptoms usually begin in adolescence to early adulthood and usually worsen slowly. The severity of symptoms vary greatly, from very mild to completely disabling Early in the disease, it causes severe weakness in muscles of the face, shoulders, and back. The mouth appears rounded and puckered, as the lips stick out. It is difficult for patients to close their eyes completely or whistle. Some have difficulty chewing, swallowing, or speaking. As the shoulder and back muscles weaken, they shrink and the shoulder blade sticks out excessively (scapular winging). Patients become unable to raise their hands above their head. Unlike other muscular dystrophies, weakness is commonly worse on one side of the body than the other (asymmetric).
Eventually, hip and leg muscles become weak and shrink. As this occurs, patients become unable to stand up from squatting position without pushing through their arms (Gower’s sign), and start to walk with a waddle (Trendelenburg gait). About half of all patients are able to walk throughout their entire lives. Life expectancy is normal.
The term “congenital” refers to the disease or symptoms being present at birth. There are two known forms of Congenital MD, Fukuyama CMD and CMD with merosin deficiency. The congenital muscular dystrophies affect males and females, causing muscle weakness and severe joint stiffness (contractures) at birth or in early infancy. Newborns with either form are often floppy (hypotonic) at birth. Head and brain malformations occur in the Fukuyama form of CMD, causing a small head (microcephaly), mental retardations, and often seizures.
Emery-Dreifuss muscular dystrophy is a rare form of MD that affects only males. Symptoms may begin in childhood or adolescence. The condition causes slowly progressive (worsening) weakness in the muscles of the shoulders, upper arms, and lower legs. Joint stiffness (contractures) Life threatening heart problems commonly occur in those with this form of MD. These heart problems may also occur in carriers of the gene that causes Emery-Dreifuss MD (people who have the gene for the disease, but do not have other symptoms).
Muscular dystrophy cannot be prevented. There is no specific treatment or cure for the disease. Care of those with muscular dystrophy is mainly focused on preventing and treating its complications, and improving the quality of life of affected children. Multiple pediatric specialists, including orthopedic surgeons, physical therapists, cardiologists, pulmonologists, nutritionists, and physical medicine specialists, make up the team that provides the necessary care to achieve this.
Each child is thoroughly evaluated and a treatment plan is determined based on their individual diagnosis and prognosis. Nationwide Children’s program has enabled our pediatric patients to live more comfortably, be more productive, and in many cases, live longer lives.