Muscular Dystrophies in Children
What is Muscular Dystrophy?
Muscular dystrophy (MD) is a genetic disease caused by a change or mutation in 1 of the genes located on the chromosomes (DNA) in human cells. Muscular dystrophy causes muscle weakness and a decrease in muscle mass over time. It can affect people worldwide of all races and ages. Nine types of dystrophies have been identified, and many types have variations or subtypes, resulting in more than 30 different forms. Several types of dystrophies affect children, and symptoms of the disease might begin in children at any time from birth to the teen years.
In children, boys are affected more often than girls, although girls may exhibit some of the effects of MD or be carriers of the disease. Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy in children, occurring in approximately 1 in 3,500 to 6,000 boys born in the United States each year. Many other forms of MD exist in children, and the exact number of children who have some type of dystrophy is not known. While no cure exists for any of the dystrophies, many treatments, including physical therapy, can help maintain function by managing complications of disease progression, such as weakness and contractures. Each child who has MD has unique needs based on age, the type of dystrophy, and the progression of symptoms. Physical therapists will work with the child and family as well as other health professionals to develop an individualized treatment plan to help the child reach full potential.
All muscular dystrophies are caused by a change or mutation in 1 of the genes located on the chromosomes (DNA) in human cells. The genes determine a person’s characteristics and traits, and the particular genes that cause MD control the proteins that are critical to muscle health. The word “dystrophy” comes from words that mean “difficult or faulty nourishment. When the MD mutation is present in the genes, a protein in muscle cells, dystrophin, is changed or missing or not produced in sufficient amounts. Proteins are essential for muscle cell health, and when they do not function properly, the muscle has an inability to repair itself and becomes weaker.
Muscular dystrophy may also occur from a spontaneous mutation when a baby is forming; that mutation will not be found in the genes of either parent. Many dystrophies result from a spontaneous mutation.
Also, the parents may be carriers of the abnormal gene. Muscular dystrophies may be inherited in 3 ways:
Autosomal dominant inheritance occurs when a child receives a normal gene from 1 parent and a defective gene from the other parent, who usually has the disorder. Each child has a 50% chance of inheriting the gene, and males and females are equally at risk.
Autosomal recessive inheritance means that both parents carry and pass on the defective gene. Each parent has 1 defective gene, but neither parent is affected by the disorder. Each child has a 25% chance of inheriting both copies of the defective gene and developing MD. Each child also has a 50% chance of inheriting 1 gene and becoming a carrier of MD, with the ability to pass the dystrophy on to their children. Males and females are equally at risk.
X-linked (or sex-linked) recessive inheritance occurs when a mother carries the MD gene on 1 of her 2 X chromosomes and passes that gene to her son (males always inherit an X chromosome from their mother and a Y chromosome from their father, while daughters inherit an X chromosome from each parent). Sons of carrier mothers have a 50% chance of inheriting MD. Daughters also have a 50% chance of inheriting the defective gene, but they also inherit a healthy X chromosome from the father and usually do not have MD. Fathers with the defective gene cannot pass an X-linked disorder to their sons, but daughters may be carriers and may pass the gene on to their children. Girls who are carriers may exhibit milder symptoms of MD.
Signs and Symptoms
All dystrophies are genetic and progressive, cause muscle weakness, and cause children to experience activity limitations and participation restrictions.
All dystrophies cause muscle weakness that gets worse over time and leads to muscle wasting. Many dystrophies cause contractures (shortening due to tightness) of joints, the curvature of the spine, respiratory (breathing) and cardiac (heart) problems, and other symptoms.
Any delay in motor milestones—the ability of the child to learn how to sit up, crawl, walk, and run at typical ages—should be investigated to determine the cause of the delay. The Gowers sign, a medical term describing the way a child gets up to stand by pushing with hands on the thighs, is often the first indication of pelvic muscle weakness. This sign is highly associated with Duchenne MD. Research has suggested that any child who continues to turn onto his stomach before getting up from the floor after 3½ years of age should be examined for weakness.
How Is It Diagnosed?
The Centers for Disease Control and Prevention state that some muscular dystrophies are not identified until a child is 3 to 6 years of age, but these disorders could be diagnosed earlier. Often, parents must wait 1 to 2 years to obtain an accurate diagnosis even after symptoms of weakness are present. Seeking treatment as early as possible and advocating for care by experts in movement disorders can make a difference in helping a child with muscular dystrophy reach full potential.
Diagnosis of MD is typically made by a physician, who may:
Order blood tests to determine levels of the muscle protein and other factors, or notice that a blood test ordered for other reasons shows an alteration in muscle proteins.
Refer to specialists for genetic testing and counseling.
Conduct a muscle biopsy.
Genetic testing is particularly helpful if a history of MD is present in the family over several generations, and genetic counseling can help parents determine if they are carrying 1 of the mutated genes that cause the disorder. Tests during pregnancy carry some risk, but may help expectant parents find out if a child has MD when a genetic history is present or suspected. Likewise, newborn screening should be completed when the family has a history of MD.
Diagnostic imaging, strength and exercise testing, electromyography studies, and other diagnostic methods may be available for diagnosing varying types of dystrophies, and new tests are constantly being developed.
How Can a Physical Therapist Help?
The physical therapist is an important partner in health care and fitness for anyone diagnosed with MD, and physical therapy should begin as soon as possible after diagnosis and before joint or muscle tightness has developed. Physical therapists identify muscle weakness and work with each child to keep muscles as flexible and strong as possible, help reduce or prevent contractures and deformities, and encourage movement and mobility for optimal function throughout all the stages of life. Each treatment plan is designed to meet the child’s needs using a family-centered approach to care. If assistive devices are needed, the physical therapist may collaborate with other professionals to determine the best walking aids, braces, or wheelchair for each child.
Evaluation. The child’s physical therapist will perform an evaluation that includes a detailed birth and developmental history. The physical therapist will also ask about the child’s overall health, and about any parental concerns. The physical therapist will conduct a physical examination, and perform specific tests to determine the child’s motor development, such as sitting, crawling, getting up to standing, and walking. Physical therapists know the importance of addressing the child’s needs with a team approach where all of the health care professionals provide holistic care that ensures mobility throughout the lifespan.
Treatment. Physical therapists work with children who have MD to prevent or reduce joint contractures, maintain or improve cardiorespiratory and muscle strength, adapt activities or the environment to promote movement and mobility skills and increase daily activities, which encourages participation in the community.
Passive and active stretching. Your physical therapist will assist you and your child in increasing joint flexibility (range of motion) and preventing or delaying the development of contractures. Passive stretching should not be painful.
Maintaining strength. Your physical therapist will teach you and your child exercises to maintain muscle and trunk strength and to use good posture and body mechanics throughout the lifespan. The therapist will identify games and fun tasks that promote strength. As the child grows, the therapist will identify new games and activities to reduce the risk of obesity, and increase heart health. Overexercising can damage muscles, so families are encouraged to seek physical therapy services early in order to identify the best strengthening activities for the child.
Exercises for breathing. The physical therapist may provide a program to maintain good respiratory strength or may work with respiratory therapists or speech therapists in designing such a program.
Improving developmental skills. Your physical therapist will help your child learn to master motor skills, such as crawling, getting up to standing, walking, and jumping. Your therapist will provide an individualized plan of care that is appropriate based on your child’s developmental level and motor needs.
Foster physical fitness and activity. Your physical therapist will assist in determining the specific exercises, diet, and community involvement that will promote good health. When needed, mobility aids, such as wheelchairs, splints and braces, and home devices may be prescribed to help maintain mobility.
Therapy may be provided in the home or at another location, such as a community center, school, or a physical therapy outpatient clinic. The child’s needs vary greatly as the child ages. The physical therapist will work with other health care professionals, including speech/language pathologists or occupational therapists, to address all the individual’s needs as treatment priorities shift.
Can this Injury or Condition be Prevented?
Genetic counseling is important for families that have a known, inherited dystrophy. However, many spontaneous mutations can result in muscular dystrophy. Excellent prenatal care is important for all pregnant women, and some women may want to be tested for specific diagnoses that can be detected during early pregnancy, including MD. Tests during pregnancy carry some risk and usually are indicated if a family history of MD exists. Once a child is diagnosed with MD, the physical therapist and other health care professionals will provide education and therapeutic techniques to prevent or reduce some of the additional complications that might occur following birth, such as developmental delay, poor strength and posture, contractures, and abnormal movement or walking patterns.
Real Life Experiences
Darius is a 4-year-old boy recently enrolled in preschool. During his first week at school, his teacher noticed he had difficulty getting up from the floor after storytime. He turned over onto his stomach and used his arms to push on his legs and stand up. The teacher asked a visiting physical therapist to watch Darius stand up. The physical therapist recognized this standing pattern as a Gowers Sign suggesting muscle weakness.
That evening, the teacher and the physical therapist spoke with Darius’s parents, who said they were concerned that Darius seemed weaker than his siblings. With parental permission, the physical therapist contacted Darius’s primary physician and shared her observation. Following diagnostic testing, the physician diagnosed Duchenne muscular dystrophy and referred Darius for physical therapy treatment.
Darius’s physical therapist developed an individual home-exercise program for him, designed to maintain strength in the muscles of his arms, trunk, and legs and to promote heart and lung health. She taught the program to his parents, and encouraged the family to do gentle exercises and stretches together every day. The physical therapist prescribed foot braces to wear during sleep at night to keep ankle range of motion. She cautioned the family to avoid over-exercising and not to wear the braces in the daytime as braces could interfere with Darius’s walking and balance. She also provided ideas to adapt activities for his participation in community events.
In the coming months, Darius’s physical therapist will help him and his family:
Be as independent as possible within the limits of the disease.
Engage in activities that maintain strength and minimize muscle weakening.
Use an individualized education plan (IEP) to integrate him into school.
Adapt physical education or other school activities as needed to ensure full integration with peers.
Choose equipment to meet his home, school, and community mobility requirements.
Learn about the disease characteristics of DMD at different ages and the new treatments being developed.
Know and use such resources as the Muscular Dystrophy Association.
Promote healthy and fun activities.