Muscular dystrophy - limb-girdle type
Limb-girdle muscular dystrophies include at least 10 different inherited disorders that initially affect the muscles around the shoulder girdle and the hips. These diseases are progressive and may involve other muscles over a period of time.
Causes, incidence, and risk factors
This is a large group of genetic diseases featuring muscle weakness and wasting (muscular dystrophy). Most are inherited in an autosomal recessive manner (both parents must have the defective gene for a child to inherit it), but some are autosomal dominant (only one parent needs to carry the bad gene to affect the child). For some of these conditions, the defective gene has been discovered, but for others, the gene is not yet known.
Typically, onset of pelvic muscle weakness (difficulty standing from a sitting position without using arms, difficulty climbing stairs) starts in childhood to young adulthood. Later there is the onset of shoulder weakness with progression to significant loss of mobility or wheelchair dependence over the next 20-30 years.
An important risk factor is having a family member with muscular dystrophy.
- Muscle weakness in pelvis, hips, upper legs, shoulders
- Loss of muscle mass in the same areas, thinning of those body parts
- Low back pain
- Abnormal, sometimes waddling, gait while walking
- Later in disease, there can be facial muscle weakness
- Later in the disease, muscles of the lower legs, feet, lower arms, and hands can become weak
- Late in the disease, there can be contractures of joints (they become fixed in a contracted position)
- Palpitations or passing out spells can be caused by abnormal heart rhythms
- Sometimes the calves will look large and muscular (pseudohypertrophy), but they are actually not strong
Signs and tests
- Normal muscle biopsy for dystrophin (the protein that is defective in the more common Duchenne muscular dystrophy)
- Electromyogram (EMG) testing shows a pattern called myopathy, sick and dying muscle fibers
- High blood creatine kinase levels
- Muscle biopsy shows degenerating muscle with splitting of muscle fibers and presence of cells of the immune system (phagocytes), which are not normally present
- In some less common muscular dystrophies, the heart may show weakness on echocardiogram (heart failure) or abnormal rhythm on ECG
There are no known treatments that directly reverse the muscle weakness. Gene therapy may become available in the future. Supportive treatment can decrease the complications of the disease.
The Muscular Dystrophy Association is an excellent resource (800-572-1717).
This is a large group of related but distinct diseases. In general, it is expected that there will be slow progression of weakness, which worsens in affected muscles, spreads, and progresses further.
Heart muscle weakness and the tendency to have abnormal electrical activity of the heart can increase the risk of palpitations, fainting and sudden death. Most patients with this group of diseases live into adulthood, but do not reach their full life expectancy.
- Progressive weakness, which results in requiring a wheelchair
- Difficulties with activities of daily living due to shoulder weakness
- Contractures due to decreased muscle movements and joint use
- Abnormal heart rhythms
Calling your health care provider
Call your health care provider if you or your child note weakness while rising from a squatting position. Call a geneticist if you or a family member have a diagnosis of muscular dystrophy and you are planning a pregnancy.
Genetic counseling may help prevent some cases. Some of the complications can be prevented by appropriate treatment. For example, a cardiac pacemaker or defibrillator can significantly reduce the risk of sudden death due to an abnormal heart rhythm. Physical therapy may be able to prevent and/or delay contractures.
by David A. Scott, M.D.