What is Duchenne Muscular Dystrophy?

 

Duchenne Muscular Dystrophy (DMD) affects about 300,000 boys worldwide.

DMD is a form of muscular dystrophy that is caused by a mutation of the dystrophin gene—located on the X chromosome—which codes for the protein dystrophin. The absence of dystrophin in the body causes muscles to deteriorate and break down. DMD is the most frequently occurring and one of the most rapidly progressive childhood neuromuscular disorders. Due to the way DMD is inherited, boys are primarily affected.


In Duchenne Muscular Dystrophy, the child’s exons (sections of DNA that code for the protein dystrophin) are deleted, duplicated, or cause an abrupt stop in the protein production process. The impaired exons then interfere with the rest of the gene being pieced together, which results in a mutation that causes the body to lack the protein needed to protect and rebuild muscle fibers. This leads to continuous muscle degeneration and premature death.

 
 

What Are The Causes?

DMD is caused by a defect in one of the genes in the body. Doctors call this a mutation.

The largest gene in our bodies contains the instructions for making a protein called dystrophin. Dystrophin is found in all muscles in our bodies and plays an important role in protecting our muscles while they are working.

All the genes in our bodies are packaged into ‘groups’ called chromosomes. These chromosomes are inherited from our father and mother.

If you are a girl, you have two X chromosomes (one X from your mother and one X from your father). If you are a boy, you have one X chromosome (from your mother) and one Y chromosome (from your father).

The dystrophin gene is only located on X chromosomes. As boys only have one X chromosome, DMD is much more common amongst boys.


In two thirds of cases, the faulty dystrophin gene is passed from the mother to the child. These women are called ‘carriers’ because they carry the DMD gene although they do not have DMD themselves. 

In one third of cases, a spontaneous mutation happens at the beginning of the pregnancy.

No one is to blame for either inherited genes or spontaneous mutations. There is nothing that anyone could have done before, during or after the pregnancy to prevent a child from developing DMD.


Genes are very complicated and sometimes they go wrong.

 

What Are The Symptoms?

DMD is rarely diagnosed at birth. Typically, it is diagnosed when the child is between 2 and 5 years old.


When you are looking for signs that a child may have DMD, you should watch them running and getting up from the floor. Muscle weakness is more noticeable during these activities.


Symptoms can include:

Delay in the ability to sit and stand independently

Large calf muscles (pseudohypertrophy)

Trouble running and jumping

Unusual gait when walking

Using the Gower's Manouevre to get off the floor (where the child has to use their hands and arms to "walk" up their own body from a squatting position due to lack of hip and thigh muscle strength)

 

The Stages of DMD

Diagnosis can be a time of terrible shock and devastation. But the prognosis for children with Duchenne is considerably better now than it was ten years ago. As therapies become better targeted and treatments are developed, prospects will improve further.

There are different stages to DMD, and how you care for children with it changes over time.

Each child is different and their journey is unique, some will hit stages earlier or later than others but here is a rough guide to what you can expect

 

Early Ambulatory

Duchenne often becomes noticeable at the stage that children begin to move around more. Children usually reach physical milestones like crawling or walking later. Getting up from the floor or from lying down may be difficult - they may resort to supporting themselves with their hands and thighs to stand upright (sometimes called Gowers' sign). They may walk more on their toes than other children. They may appear clumsy, fall more often, and have problems with climbing, jumping or running. There may be slower speech development. They may appear more tired than other boys.


The effects of the disease are first seen in the leg muscles. Calf muscles may appear to be enlarged or swollen. This is called pseudohypertrophy. Damaged muscle cells are replaced by fat and scar tissue which is called fibrosis.


Learning or behavioural difficulties may appear at this stage. These will range from none at all, to very slight, to more significant. These usually remain static and do not increase as the disease progresses.

Suggestions

 - a test to identify the specific genetic mutation to help choose treatment options and trials

 - diet and weight checks

 - physiotherapy and stretching

 - night splints

 - discuss starting cortico-steroids to promote muscle strength

 - supplements

 - choosing the right schools to support your child's needs

 - emotional support for the parents

 - advice on explaining the diagnosis to friends and family 

 - application for an EHC (Education & Healthcare Plan) from your local authority

 - referral to speech therapy (if necessary) 

 - consider DEXA scans to monitor bone strength

Late Ambulatory

Children at this stage will still be able to move around by themselves, but it will become increasingly difficult. As the thigh muscles weaken further, walking becomes harder. Children's balance may be affected, which may lead to a change in posture. They may walk on the balls of their feet or their toes more than other children.  Walking will become harder and boys may tire more quickly. Climbing up and down stairs will become harder.

Suggestions

 - walking aids: mobility scooters, walkers, or a lightweight wheelchair for longer distances

 - night splints

 - cortico-steroids and supplements

 - regular echocardiogram tests for the heart

 - heart medication (ace inhibitors, beta blockers)

 - regular lung function tests (including the Forced Vital Capacity measurement and peak flow)

 - non-prescribed supplements

 - exercise - discuss with clinical staff how it is best to exercise

 - physiotherapy and stretching

 - schools - consider which will support your needs best

 - application for a statement of educational needs

 - clinical trials - often the best access point for the newest drugs

 - wheelchair, lift and stairlift funding for the home and at school

 - application for advice and grants to adapt the home

 - blue badge disability parking permit application

 - consider DEXA scans to monitor bone strength

 - cough assist machine (if required)

Early Non-Ambulatory

DMD children will lose the ability to walk independently and will start using a wheelchair on a more regular basis. They will still be able to use their arms to propel themselves around, but increased weakness will start spreading to the arms and neck. They will continue to be able to use their arms and fingers so they will still be able to write and use a computer. 


Lungs will weaken, which may lead to difficulties with breathing. Breaths may become shallower, and the ability to cough lessens. This may lead to more chest infections because it's harder to clear mucus and germs from the chest. As breathing weakens, oxygen levels in the blood may fall, leading to tiredness, irritability, headaches on waking, inability to sleep and vivid dreams. Breathing respirators, and cough assist technologies can help with this. In time, support will be needed breathing, first overnight and then during the daytime.


The heart muscles will also be affected. This is called cardiomyopathy, and there are treatments available to help.

Suggestions

 - physiotherapy to remove mucus from the chest

 - non invasive ventilation

 - techniques to increase the air flow into the lungs

 - breathing respirators

 - hoists

 - monitor for scoliosis

 - bone drugs (bisphosphonate treatments)

 - regular echocardiogram tests for the heart

 - heart medication (ace inhibitors, beta blockers)

 - promoting independence

 - support for frustration, anger and emotional distress

 - respite for carers

 - ask consultant about a sleep study (if sleepy in the day or headaches)

 - DEXA scans to monitor bone strength

Late Non-Ambulatory

Life expectancy is improving so there are more people with Duchenne muscular dystrophy who are in their thirties and forties. But as muscles weaken, paralysis will set in. Young adults may have difficulty chewing and swallowing food, this is called dysphagia. If it is severe, a feeding tube into the stomach may be needed. They will need help eating, drinking, going to the toilet, dressing, washing and being moved into bed and being turned in bed.


Many young adults continue to be able to use their fingers well into adult life. Their ability to talk usually remains good, and can be helped with speech therapy and speech amplification equipment. Their ability to be able to think for themselves is unimpaired and, with support, adults with Duchenne muscular dystrophy can play an active part in society. 

Suggestions

 - good access to computer technology

 - discussions about implementing independent living

 - finding and keeping a job

 - identifying and managing depression

 - encouragement of emotional support outside the family in friendship groups.

 

Help Us Find A Cure For Duchenne