Duchenne /Becker Muscular Dystrophy (DMD / BMD)
DMD / BMD are the most common neuromuscular disease. This genetic disorder characterized by progressive muscle degeneration and weakness due to the mutation in gene called Dystrophin that helps keep muscle cells intact. DMD symptoms onset is in early childhood between age 2 -3 years. The disease primarily affects boys, but in rare cases it can affect girls. Treatments are available for management of symptoms and improve quality of life.
- Progressive muscle weakening and wasting
- Bulky calf muscles
- Difficulty in sitting, standing, walking
- Frequent falls
- Learning difficulties
- Weakness in legs, arms, pelvis, neck which rapidly worsens
- Failure to develop motor skills
- Heart and respiratory muscles are also affected
Genetics of the Disease
Gene - DMD
Inheritance - X linked Recessive
Penetrance (probability of occurrence if defective gene is present)
Male – 100% Female – varies (depends upon X chromosome inactivation)
All the gene in our bodies are packed into ‘groups’ called chromosomes. These are inherited from our father and mother. The dystrophin gene is located on X chromosome. Boys have only one X chromosome inherited from mother thus are more commonly affected with DMD. Whereas girls have two X chromosomes, each inherited from mother and father, thus girls are mostly carriers.Girls can also develop DMD under rare circumstances if both of her X chromosomes become faulty either by de-novo mutation during pregnancy or skewed X inactivation (inactivation of X chromosome with healthy gene).
In 1/3 cases, a de-novo mutation happens at the beginning of the pregnancy. Genes are very complicated and sometimes they go wrong. Hence no one is to blame for either inherited or de-novo defects.
Testing for DMDYour doctor is likely to start with medical history and physical examination. Genetic counsellor might recommend you following tests:
Enzyme test – Damaged muscles release enzymes, such as creatine kinase (CK), into your blood. In a person who hasn’t had a traumatic injury, high blood levels of CK suggest a muscle disease.
Genetic Test – Blood samples can be examined for mutations in DMD gene that causes DMD/BMD
Multiplex ligation dependent probe amplification (MLPA) – This is first tier genetic test for diagnostics or carrier screening for DMD. Test is also performed on prenatal samples with risk for known familial DMD deletion or duplication. If no deletions or duplications are detected or no result explains the clinical scenario, sequencing of the DMD gene is performed.
70% DMD/BMD patients are with deletions/duplication
Sanger Sequencing – Identifies point mutations in DMD gene. Test is performed on samples with known familial variant.
30% DMD/ BMD patients are with point mutations
Next Generation Sequencing – Recommended for diagnostics test or carrier screening for DMD / BMD
Muscle biopsy. A small piece of muscle can be removed through an incision or with a hollow needle. Analysis of the tissue sample can distinguish muscular dystrophies from other muscle diseases.
Heart and Lung monitoring tests: These tests are used to check heart function and lung function especially in people diagnosed with myotonic muscular dystrophy.
Electromyography. An electrode needle is inserted into the muscle to be tested. Electrical activity is measured as you relax and as you gently tighten the muscle. Changes in the pattern of electrical activity can confirm a muscle disease.
Although there is no cure for any form of muscular dystrophy, treatment for some forms of the disease can help extend the time a person with the disease can remain mobile and help with heart and lung muscle strength. Trials of new therapies are ongoing. People with muscular dystrophy should be monitored throughout their lives. Their care team should include a neurologist with expertise in neuromuscular diseases, a physical medicine and rehabilitation specialist, and physical and occupational therapists.
Several types of therapy and assistive devices can improve the quality and sometimes the length of life in people who have muscular dystrophy. Examples include:
Physical Therapy: Muscular dystrophy can restrict the flexibility and mobility of joints. Limbs often draw inward and become fixed in that position. Range-of-motion exercises can help to keep joints as flexible as possible. Low-impact aerobic exercise, such as walking and swimming, can help maintain strength, mobility, and general health. Some types of strengthening exercises also might be helpful. But it's important to talk to your doctor first because some types of exercise might be harmful.
Braces: Braces can help keep muscles and tendons stretched and flexible, slowing the progression of contractures. Braces can also aid mobility and function by providing support for weakened muscles.
Mobility aids: Canes, walkers, and wheelchairs can help maintain mobility and independence.
Respiratory Therapy : As respiratory muscles weaken, a sleep apnea device might help improve oxygen delivery during the night. Some people with severe muscular dystrophy may need a ventilator to breathe.
Occupational Therapy: It can help patients relearn lost motor skills like swallowing difficulties, using assistive devices, such as wheelchairs, eating vessels and personal items like brushing, combing etc.
Testing available at Variant Genetics
Diagnostics Testing (Blood sample) – MLPA
Diagnostics Testing (Blood sample) – Sanger Sequencing
Prenatal genetic Testing (chorionic Villus Sampling (CVS) – 11 weeks into pregnancy
Prenatal genetic Testing (amniocentesis) – 15 weeks into pregnancy
Carrier Testing (Blood sample) – MLPA
Carrier Testing (Blood sample) – Sanger Sequencing
Why Variant Genetics
- Expert team of Medical Genetics Scientists
- Genetic Counselling Facility
- No hassle testing
- Use of latest technology
- Real time consultation and updates
- Highly scalable – flexible number of samples
- Competitive Prices
- Competitive TAT
- Unparallel customer support
* Blood * Cheek Swab * Saliva * Amniotic Fluid * Chorionic Villus
There are no major risks associated with diagnostic test or carrier testing. Prenatal testing has small risk of miscarriage (1:200-400).