Becker muscular dystrophy (BMD) is a condition in which skeletal and heart muscles slowly degrade.
The causes and symptoms of BMD are similar to those of Duchenne muscular dystrophy (DMD), though the disease’s progression is typically slower. BMD is named after Peter Emil Becker, the German doctor who first described the differences between this disease and DMD in the 1950s.
BMD is an inherited disease that is primarily seen in men, although women can be carriers of the genetic mutation responsible for causing the condition and pass it onto their children. Experts estimate that BMD affects between 1 in 18,000 and 1 in 30,000 boys and men. The first symptoms of the disease can appear as early as age 5, or as late as adulthood.
What causes BMD?
Like DMD, BMD is caused by a mutation in the DMD gene.
In BMD, the genetic alteration causes the body to produce fewer or less functional dystrophin proteins. Dystrophin provides structural support and protection to muscle fibers, so an inadequate amount of it leads to muscles starting to deteriorate. Because BMD can be caused by multiple mutations of the DMD gene, the severity of the disease can vary greatly among patients.
How does BMD affect the body?
Muscle weakness in the legs, trunk, and pelvis are usually the first symptom of BMD. This causes difficulty in running, jumping, and walking with a normal gait. Patients with more severe symptoms may eventually require a wheelchair.
Although most BMD patients experience muscle deterioration only in skeletal muscles, the condition can affect the heart muscle, too — as in DMD. Although BMD generally does not affect life expectancy, its cardiac symptoms can be life-threatening if not addressed.
How is BMD diagnosed?
Doctors can suspect BMD if a person has muscle deformities, abnormal bone development, or a heart condition called cardiomyopathy. Laboratory and muscle tests may be requested for a definitive diagnosis of BMD.
Blood tests typically measure blood levels of creatine kinase, an enzyme that is released from damaged muscles. Electromyography (EMG) measures muscles’ ability to contract when stimulated. The tests are not enough on their own to diagnose BMD. Doctors can prescribe genetic tests to look for specific mutations in the DMD gene. Doctors can also recommend a muscle biopsy to look for the presence of dystrophin protein.
How is BMD treated?
There is no cure for BMD. Several treatments can help reduce the severity of the symptoms and improve patients’ quality of life.
Regular physical activity, physical therapy, and corticosteroids can counter muscle weakness, though corticosteroids can often have harsh side effects. Scientists are developing experimental therapies to address the genetic causes of the disease and to offer long-term relief of symptoms. These approaches include stop codon read through and gene therapy.
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