Becker muscular dystrophy or BMD is a type of muscular dystrophy, a genetic condition that weakens and damages muscles. It can worsen with age.
However, its symptoms are less severe than Duchenne muscular dystrophy, which is more common.
What Is Becker Muscular Dystrophy?
Becker muscular dystrophy is one of the nine types of muscular dystrophy. It was named after the German doctor Peter Emil Becker, who identified it in the 1950s. It is a genetic disorder that causes muscle weakness and damage. It belongs to a group of muscular dystrophies called dystrophinopathies.
Dystrophinopathies, including Becker muscular dystrophy (BMD) and Duchenne muscular dystrophy (DMD), occur when there are certain mutations in the genetic code. One gene, for instance, controls the production of dystrophin, a protein that protects muscle fibers from damage. A change in this gene results in limited or discontinued dystrophin production.
If you have Becker muscular dystrophy, your body produces abnormal levels of dystrophin. A lack of dystrophin makes your muscle fibers prone to damage by enzymes or other proteins. This leads to muscle degeneration.
If you have Duchenne muscular dystrophy, your body produces little or no dystrophin. Symptoms are more severe than those of Becker muscular dystrophy.
What Are the Causes of Becker Muscular Dystrophy?
Becker muscular dystrophy occurs when there’s a change or mutation in the gene that produces dystrophin. The mutation can occur randomly, or it can be inherited from your parents. If you have this mutation, the gene produces less dystrophin than you need. Without dystrophin, your muscle cells remain unprotected and are at risk of damage.
Becker muscular dystrophy is a genetic disorder linked to the X chromosome. The dystrophin gene that causes it inhabits the X chromosome.
Because males have only one X chromosome, they’ll only receive one copy of the dystrophin gene. If they inherit the changed or mutated dystrophin gene from a parent, their body will only produce abnormal dystrophin.
Females carry two X chromosomes, meaning they’ll have two copies of the gene. Even if one X chromosome has the mutated gene, the other one can produce normal dystrophin protein.
This is why Becker muscular dystrophy affects males more often than females. Also, females tend to have milder symptoms than males.
However, females can be carriers. Even if they don’t have symptoms, they have a 50% chance of passing it on to their children without knowing it.
What Are Becker Muscular Dystrophy Symptoms?
Becker muscular dystrophy symptoms can be mild, but the condition is progressive and worsens with age.
The main symptoms include muscle weakness and loss of muscle mass. It primarily affects voluntary muscles: i.e., muscles that you can move at will, like the hip, pelvic, thigh, and shoulder muscles. It doesn’t affect your bladder or bowel muscles.
If you have Becker muscular dystrophy, you may have trouble moving your muscles. You may not be able to walk fast, climb stairs, or lift heavy things. It can also affect your heart muscles, which can cause various complications.
Symptoms can start at any age from 5 to 60 years, but they vary from person to person. If you have Becker muscular dystrophy, you may waddle while walking, walk on your toes, or stick your abdomen out to compensate for weak muscles.
Children with Becker muscular dystrophy may also start walking later than other kids. Muscle weakness in the hips and pelvis sets in early as age 10. You may even notice walking problems by the time your child is 15 or 16 years old. Children who show symptoms at a younger age are at a higher risk of heart problems than those who show symptoms later.
In cases of Becker muscular dystrophy, you may not feel any muscle pain, but you can get cramps, which typically go away with medication.
As mentioned, people with Becker muscular dystrophy can also develop cardiac problems like cardiomyopathy or heart muscle damage. This side effect is rare but dangerous. Heart problems due to Becker muscular dystrophy can be life-threatening even in teenagers. If you have the condition, it’s best to avoid strenuous exercise as it can further damage weak heart muscles.
Becker muscular dystrophy doesn’t initially affect lung muscles, but they can become weaker over time.
A lack of dystrophin can even affect your brain. It can cause neurological and behavioral problems. However, people with Duchenne muscular dystrophy show more severe neurological symptoms.
How Is Becker Muscular Dystrophy Diagnosed?
If you have symptoms of Becker muscular dystrophy, your doctor will physically examine you. They will use muscle tests and lab tests. They’ll also check your medical history and family history.
Doctors use the following tests to diagnose Becker muscular dystrophy:
Creatine phosphokinase blood test. This test checks levels of a muscle protein called creatine phosphokinase (CPK), also called creatine kinase. When you have Becker’s muscular dystrophy, your muscle cells break down and release CPK into your blood. High levels of CPK indicate that you have the condition.
Electromyography. This involves checking the strength of electrical signals from your brain to your muscles using special needles. The needles record the electrical activity, which is displayed on a computer. Abnormal patterns indicate muscle damage.
Muscle biopsy. A biopsy involves collecting a sample of muscle tissue, usually from the thigh, to check its dystrophin levels. If there's no dystrophin, you have Duchenne muscular dystrophy. However, if there are small amounts of dystrophin, you have Becker muscular dystrophy.
Genetic testing. Doctors take your tissue samples to study your genes. They check if your dystrophin gene has a change or mutation.
Western blot test. Doctors use this lab test to measure dystrophin levels in your muscle cells and check the severity of the disease.
What Is Becker Muscular Dystrophy Treatment and Management?
There's no known cure for Becker muscular dystrophy. Doctors use the following treatments to manage the condition:
- Ankle or foot braces, scooters, wheelchairs, or other physical aids to help in movement
- Occupational and physical therapy
- Medication for heart problems
- Regular monitoring of the heart’s condition
- Surgery or a heart transplant in cases of severe cardiomyopathy
Doctors must be careful with anesthesia, though, as it can cause complications in people with Becker muscular dystrophy.