Muscular dystrophy

Overview

Muscular dystrophy (MD) is a group of disorders that affects voluntary muscles, mainly those around the hips and shoulders. MD can affect people at any age. The most common type seen in children is Duchenne muscular dystrophy, which affects an estimated 1 in 3,500 boys worldwide. UCSF's Neuromuscular Clinic has been recognized as a Certified Duchenne Care Center — signifying a center that provides high-quality, comprehensive care for Duchenne MD — by Parent Project Muscular Dystrophy.

Over time, children with MD lose muscle bulk and strength. Eventually, children may need a power wheelchair or scooter, especially for long distances. The heart and breathing can also become affected as the condition progresses.

MD is caused by a problem with genes that are involved in making proteins needed for proper muscle function. When protein problems arise because one of these genes is faulty, the muscle fibers don't work correctly. Gradually, the muscles become weak enough that people experience symptoms. The protein that is affected determines how fast the disease progresses, and if problems will arise in the heart or with breathing.

Signs & symptoms

The main symptom of all MD disorders is progressive weakening of the muscles. Otherwise, the symptoms and the age they appear can vary depending on the type of MD. Common early symptoms include:

• Difficulty walking, frequent falls or toe walking
• Difficulty rising from a seated position or from the floor without using the arms (called a Gower's maneuver)

Diagnosis

In diagnosing any form of muscular dystrophy, doctors usually begin by taking a patient and family history and performing a physical examination. Occasionally, patients will undergo electromyography, a test that looks at the electrical activity of the muscles and nerves, to see where the problem lies.

Levels of creatine kinase (CK), an enzyme that leaks out of damaged muscle, are often evaluated with a blood test. When elevated CK levels are found, it usually means muscle is being destroyed by some abnormal process, such as a muscular dystrophy or inflammation. Therefore, a high CK level suggests that the muscles themselves are the likely cause of the weakness, but it doesn't determine what the muscle disorder might be.

Today, DNA testing for genetic flaws that are known to cause MD is available for many forms of the disease. If a particular type of MD is suspected, DNA testing, using a blood sample, may be performed relatively early in the diagnostic process. In some cases, the doctor must order a muscle biopsy, the surgical removal of a small sample of muscle from the patient.

Using a variety of techniques, muscular dystrophies can be distinguished from inflammatory and other disorders. Specific testing of the biopsy may also distinguish among different forms of muscular dystrophy. Genetic testing can then be performed to confirm a diagnosis.

Treatment

Medications

Currently, Duchenne MD is the only form of MD with research evidence showing that medication can be beneficial. Steroids — also called glucocorticoids or corticosteroids — are the only drugs known to slow the decline in muscle strength and motor function in DMD. The goal of steroid use is to help the child walk independently for longer, to allow more participation in everyday activities, and to later minimize breathing, heart and orthopedic problems. They can also reduce the risk of scoliosis, an abnormal curvature of the spine.

Steroids do have side effects, including weight gain, behavioral issues, bleeding in the gastrointestinal tract, high blood pressure and the development of diabetes. Children need to be followed closely when on this medication and cannot stop taking it suddenly.

Albuterol has also been tested in DMD as well as other neuromuscular disorders, and evidence suggests some mild benefit in increasing lean muscle mass. Some patients also feel an increase in energy. Albuterol has few side effects, most commonly anxiety, agitation and tremor.

Various supplements have also been tested and may be helpful for some MDs. These include antioxidants, such as coenzyme Q10, and creatine monohydrate.

Physical Therapy

People with MD need different types of rehabilitation management throughout their lives. Much of this care will be delivered by physiotherapists and occupational therapists, but other experts may be involved, including rehabilitation specialists, orthotists, providers of wheelchairs and orthopedic surgeons. Management of muscle extensibility and joint contractures is a key part of rehabilitation management.

The goal of stretching is to preserve function and maintain comfort. The stretching program will be monitored by the physiotherapist but needs to become part of the family's daily routine. There are many factors that contribute to the tendency for joints to get tight or "contracted." These include the muscle becoming less elastic due to limited use and positioning, or the muscles around a joint becoming out of balance, with one stronger than another. Maintaining good range of movement and symmetry at different joints is important. This helps to maintain the best possible function, prevent the development of fixed deformities, and prevent pressure problems with the skin.

As difficulty with walking increases, a power wheelchair should be provided sooner rather than later. With time, arm strength becomes more of an issue. Physiotherapists and occupational therapists can recommend assistive devices to help maintain independence.

It is important to think proactively about the kind of equipment that will best support independence and participation in everyday activities, and to plan ahead to provide it in as timely a manner as possible. Additional adaptations may be needed to help patients with getting upstairs and transferring from one place to another (for instance, from the bed to a wheelchair), eating and drinking, turning in bed and bathing.

Bone health is also very important, especially for children who don't stand much during the day and those taking steroids. These children have a lower bone mineral density and are at increased risk of fractures (broken bones) compared to the general population. Sometimes vitamin D and calcium are prescribed.

Pulmonary Care

Because breathing muscles can become affected as patients with MD get older, they are at risk for chest infections, often due to an ineffective cough. Later on they can develop problems with their breathing when sleeping. Some may require help with breathing during the day as well. Immunizations are recommended to decrease the chance of developing significant problems from viruses such as influenza.

As this is a staged progression of problems, a planned and proactive approach to respiratory care is possible based on appropriate surveillance, prevention and interventions. This is why the patient care team at the UCSF Pediatric Neuromuscular Clinic includes a pulmonologist and respiratory therapist with expertise in non-invasive ventilation and associated techniques for increasing the amount of air that can enter the lungs, and manual and mechanically assisted cough.

Cardiac Care

Some MDs are associated with heart problems such as dilation, leading to heart failure or electrical conduction issues. The aim of cardiac management in MD is early detection and treatment of the deterioration of heart muscle function — usually cardiomyopathy — that often occurs as some of the diseases progress.

As these problems often develop silently, without any significant symptoms, they must be watched for carefully so they can be treated promptly. Surveillance and proactive management are key. For this reason, the UCSF Pediatric Neuromuscular Clinic's patient care team includes a cardiologist.

Nutrition and Gastrointestinal Care

Nutrition and weight are key issues in keeping people with MD healthy. Some patients will develop swallowing problems. At UCSF, we work closely with a number of gastroenterologists and nutritionists to help manage these problems.