Duchenne Muscular Dystrophy: Genetic Disorder {Guide}

Duchenne muscular dystrophy is a degenerative disease that affects skeletal muscles. With over 30 different types of muscular dystrophy, learning which one you or a family member may have can be overwhelming.

At YourDNA, we aim to make the education process simple, telling you what you need to know and how to get the answers you deserve.

Were You or a Loved one Recently Diagnosed? Start Here

Receiving a diagnosis of Duchenne Muscular Dystrophy can be overwhelming. You likely received a ton of information in a short amount of time. Once things settled, you were likely left with questions. Let us start by saying, Duchenne Muscular Dystrophy is no one's fault. There is not anything someone did or did not do to cause this. Additionally, you are also not alone. There is a large community of families with this condition who can provide guidance and support. Today, there are exciting new developments for the treatment of this condition and our knowledge will only grow. Take your time moving through the sections and feel free to read it a few times. YourDNA is here for you, and we are so glad you are here.

Quick Overview

Duchenne muscular dystrophy is a neuromuscular genetic disease which causes progressive muscle weakening in patients with the disease, often rendering them unable to walk unassisted by their preteens. While it's the most commonly diagnosed type of muscular dystrophy, it's still very rare with only 400 to 600 people diagnosed with the disease annually.

What Is Duchenne Muscular Dystrophy?

Referred to as DMD, Duchenne muscular dystrophy is a degenerative disease that affects the skeletal muscles, weakening the patient over a period of several years.

Duchenne Muscular Dystrophy is a dystrophinopathy which is a spectrum of X-linked genetic conditions focusing on muscle degeneration. Specifically it is a form of muscular dystrophy called the duchenne type. It is an X-linked  genetic condition that is passed down from parent to child on the X chromosome.

Most patients are diagnosed with Duchenne muscular dystrophy very young, typically at age 2 or 3. While the progression is slow, it's always fatal, with most patients not living beyond their 20s or 30s.

With the advancements in medicine, however, some rare cases are surviving into their 40s and 50s ¹, giving hope to researchers and doctors alike that in the future patients can live a long, fulfilling life.

Is Duchenne Muscular Dystrophy Hereditary?

Yes, for the most part DMD is hereditary, passed down from a parent to a child on the X chromosome ².

Duchenne Muscular Dystrophy is an X-linked genetic condition. A male will have the condition when a gene on the X-chromosome called DMD is not working correctly. We know that females have two X-chromosomes while males have one X-chromosome and one Y-chromosome. 

As females have two X-chromosomes, they have two copies of the DMD gene, one on each chromosome. If one of their copies of DMD is not working properly, then their other working copy of DMD will be sufficient enough for them to not develop the condition.

However, they will be considered carriers and have a 50% chance of having a son with Duchenne Muscular Dystrophy and a 50% chance to have a daughter who will also be a carrier.  

If a male with Duchenne Muscular Dystrophy has children then 100% of his daughters will be carriers, while none of his sons will be affected. 

In some cases, a person may have the gene mutation without having a prior family history of the disease. In these instances, it's considered a spontaneous mutation.

The Difference Between Duchenne Muscular Dystrophy and Becker Muscular Dystrophy

Genetic changes in the DMD gene can also cause another condition called Becker Muscular Dystrophy. Depending on the specific change in the DMD gene will determine if an individual has Duchene or Becker Muscular Dystrophy. Both conditions will have symptoms displayed in muscle cells including skeletal muscles and cardiac muscles. 

Becker Muscular Dystrophy (BMD) tends to be more mild than Duchenne Muscular Dystrophy (DMD). While individuals with DMD tend to get diagnosed around 4-years-old, individuals with BMD do not get diagnosed until 14 years. Both conditions will cause progressive muscle weakness, but individuals with BMD will experience symptoms later than DMD and live longer. 

What Causes Duchenne Muscular Dystrophy?

The disease is caused by a mutation on the X chromosome, particularly in the dystrophin, or DMD gene. The dystrophin gene is responsible for making the dystrophin protein, which is required by the body to facilitate normal muscle movement ³.

It helps to strengthen and protect muscle fibers against injury.

In a patient with Duchenne muscular dystrophy, one or more portions of the gene, known as exons, are either missing, duplicated or mutated. When this happens, the exons don't fit together properly and because of this, it's unable to or has difficulty producing dystrophin.

Those diagnosed with DMD typically produce minuscule amounts of the protein, or none at all, depending on the mutation.

Signs and Symptoms of Duchenne Muscular Dystrophy

The symptoms of DMD will start presenting early in childhood. Most children with this condition will have delayed motor milestones, with an average age of walking of 18 months.

When they do walk, it is often on their toes with their legs spread apart, they might experience often episodes of falling, and are easily fatigued. By the age of 15 more than 90% of people with DMD are in wheelchairs. 

Individuals will continue to have progressive loss of muscle strength. It might appear that these individuals have enlarged calf muscles or thighs, but this is considered to be pseudohypertrophy or a “false enlargement.” 

The loss of muscle strength can lead to a number of other complications. 70-90% of patients will experience scoliosis in their early teenage years. As the muscle continues to deteriorate, contractures can develop. These occur when muscles start to harden and can lead to rigidity of joints which can lead to discomfort.

Respiratory muscles and heart muscles are also affected in these individuals. Most individuals with DMD greater than the age of 18 will experience some form of cardiomyopathy. 

Additionally, about 19% of patients experience some form of cognitive impairment. However, it is not progressive.

Who Does Duchenne Muscular Dystrophy Typically Affect?

Duchenne muscular dystrophy typically occurs in males. It's inherited through an x-linked recessive pattern, which means it's passed down from the mother to her sons.

Females who have a non-working copy of the DMD gene are a carrier of muscular dystrophy but rarely ever show symptoms. If they do, these symptoms are very mild and not usually life-threatening.

Does Duchenne Muscular Dystrophy Occur in Children?

Yes, most affected children with DMD will receive a diagnosis around 4 years of age. It can appear but is hardly ever diagnosed in infants or babies because they're too young to present symptoms.

Diagnosis of Duchenne Muscular Dystrophy

Diagnosing Duchenne muscular dystrophy requires a visit to the doctor. Your child's pediatrician tracks all of their developments through the first several years of their lives.

While every child has a different growth pattern, around the ages of 2 or 3, they should achieve certain milestones.

Because the classic symptoms of Duchenne muscular dystrophy include muscle weakness, having problems walking, standing or climbing stairs during the toddler years is often a red flag.

If your child continues to have issues, the pediatrician may refer you to a specialist such as a neuromuscular expert or a pediatric neurologist for further testing.

How Do You Diagnose Duchenne Muscular Dystrophy?

There are a few ways to diagnose Duchenne if a doctor suspects that it's the cause of the symptoms a patient presents. Each of these diagnostic measures require special testing, whether it's a blood or genetic test, or in some instances, a muscle biopsy.

How Do Doctors Test for Duchenne Muscular Dystrophy?

The most common forms of testing for Duchenne that doctors use is Creatine Kinase (CK) testing, genetic testing and muscle biopsies. The CK testing can determine whether there's a muscular problem by the amount of creatine kinase in the blood.

This enzyme leaks out of damaged muscles so high levels are of a concerning nature.

Genetic testing is done through a blood test and often follows CK testing to confirm the presence of the DMD gene mutation 4. Doctors will order genetic testing if there are high levels of creatine kinase in the blood sample as this alone is not enough to confirm a diagnosis.

Sometimes, doctors may order a muscle biopsy, whether before or after genetic testing, as this can help further confirm a diagnosis of Duchenne muscular dystrophy.

The doctors can examine the muscle tissue under a microscope and determine how much and where the dystrophin protein exists. Because genetic testing has become so advanced, muscle biopsies tend to be rarer these days.

Duchenne Muscular Dystrophy and Genetics

Much like x-linked dilated cardiomyopathy, Duchenne muscular dystrophy is passed down to children in an x-linked recessive pattern, and they're both related to the dystrophin gene ⁴.

Genetic Tests for Duchenne Muscular Dystrophy: Are They Available?

Yes, the most reliable type of genetic testing is done through a physician's office or lab, wherein a blood sample is collected and researchers look specifically for the dystrophin gene on the X chromosome. While there may be at-home DNA tests that indicate carrier status, they're not as specialized as one ordered at a doctor's request.

DNA Testing to Spot or Detect Duchenne Muscular Dystrophy Early

When it comes to early DNA testing for Duchenne muscular dystrophy, the best bet a person has is to do a carrier test prior to having children. The carrier test can tell whether you or your partner has the mutated gene and what the risk is for passing this mutation down to your future children.

DNA Tests Currently Available for Duchenne Muscular Dystrophy Include:

DNA testing is currently available through a medical laboratory, in which the test is ordered by a doctor to confirm the diagnosis of Duchenne's.

Most, if not all, at-home tests currently do not offer carrier status testing for DMD, though new additions are always being made and it's possible you'll be able to test at home in the future.

Where Can I Go For a Genetic Test For my Child?

To get genetic testing for your child, you can visit their pediatrician and express your concerns. They may refer you to a genetic counselor, particularly if there's a family history of the disease.

DNA Testing for Duchenne Muscular Dystrophy: Strengths and Limitations

All DNA tests have limitations and strengths. With genetic testing for Duchenne, if you have your DNA tested before you get pregnant, you can only learn whether you're a carrier and what odds you have of passing down the gene mutation to your future children.

Knowing that you are a carrier, does not determine if your children will or won't inherit the disease, leaving you with uncertainty. 

On the other hand, knowing if you're a carrier can help you make those important decisions as to whether you want to have children and how to potentially prepare for the fact ahead of time. Men who have the mutation won't need a DNA test because they will present with symptoms.

What Are the Chances That I Will Pass Duchenne Muscular Dystrophy on to My Child?

The risk of passing DMD onto your children depends on whether you're a male or female. Female carriers have a 50 percent chance of passing the mutation down ⁵, creating a 25 percent chance that she will have a child with DMD.

Men, on the other hand, have to have DMD to pass it down, and they can only pass it onto their daughters. These girls will then be carriers of the disease, but any sons that the male has will be unaffected as the X chromosome is only passed onto females.

If I Have One Child With Duchenne Will All My Children Have It?

No. It's perfectly possible to have children without the mutation even if one parent has it. Females can only pass it onto their sons, and this isn't a certainty, it's much like playing genetic roulette. Men can only pass it onto their daughters, who will only be carriers and likely never present with symptoms.

Testing for Duchenne Muscular Dystrophy on a Pregnancy or Before a Pregnancy Is Achieved

When you're pregnant or trying to get pregnant, it's normal to worry about all of the unknown factors. If you're concerned about your child having Duchenne muscular dystrophy, you can undergo genetic testing before and during pregnancy.

During pregnancy, your doctor will do an amniocentesis, which poses little risk to the fetus. The results can indicate whether your child has the mutation.

Before pregnancy, you can undergo genetic counseling, which often involves genetic testing, to determine what your risks are and how to plan for them in the event that you do have a child with DMD.

Additionally, if you know for a fact that you're a carrier, you can plan a pregnancy where DMD is eliminated using preimplantation genetic diagnosis and in vitro fertilization, where only eggs and sperm that are free of the mutation, deletion or duplications are used ⁶.

Is Duchenne Muscular Dystrophy Treatable?

To an extent, yes.

You can treat Duchenne muscular dystrophy, but doctors aim to make patients comfortable and prolong their life as much as they can by slowing down the rate of progression.

Duchenne Muscular Dystrophy Treatment Options

For the most part, treatment of Duchenne Muscular Dystrophy is focused on treating the various symptoms. The American Academy of Pediatrics recommends that individuals with DMD take ACE inhibitors and potentially beta blockers as well to improve cardiac function.

If someone with DMD develops congestive heart failure then diuretics will be used to try and minimize symptoms. Cardiac transplant might be available for some patients. For patients who experience scoliosis then bracing and surgery, such as spinal fusion, is recommended. 

To improve muscle disease, it is recommended that individuals with DMD between the ages of 5 and 15 engage in corticosteroid therapy through use of prednisone or deflazacort. 

One of the most exciting developments for the treatment of DMD is eteplirsen (EXONDYS 51). This is the very first FDA-approved treatment in the United States for Duchene muscular dystrophy. This drug is a form of gene therapy that uses the technology exon skipping to skip exon 51 in DMD.

Not all individuals with DMD are eligible for this drug as it depends on the patient’s specific genetic difference in DMD. However, for the 13% of genetic differences that are eligible, this drug is given as weekly infusions and has shown a 2.8X increase in the levels of dystrophin.

This is an exciting time for the treatment of DMD and the field of gene therapy. 

What Are Duchenne Muscular Dystrophy Care Options?

Since the main treatment of DMD is to keep the patient comfortable and slow down the rate of progression, they typically come up with a care plan based on the patient's symptoms.

These plans may include drugs like steroids to slow down muscle degeneration, as well as physical therapy to keep the muscles as strong as possible.

Over time, as a person's functionality decreases, the care plan should involve bringing a caretaker into the home if a parent is unable to care for the patient to the extent they need.

The Prognosis for Duchenne Muscular Dystrophy

Currently, the prognosis for DMD is not very favorable. Most patients diagnosed with it tend to only live to their 20s or 30s due to cardiomyopathy or respiratory failure.

Most are also wheelchair bound in their teens due to progressive muscle weakness and wasting that prevents them from standing for any real period of time. The Muscular Dystrophy Association (MDA) is working to fund clinical trials and research to help develop treatments and hopefully, a cure for the disease one day.

Does Duchenne Muscular Dystrophy Go Away?

No, a patient who is diagnosed with DMD will have the condition for life. Individuals with this condition will need consistent health care. It's a fatal disease that drastically affects the person's quality of life, especially toward the end when muscles weaken to the point that most cannot stand on their own.

Is There a Cure for Duchenne Muscular Dystrophy?

At this time, there is no cure for the condition. Doctors instead aim at treating the symptoms keeping comfort and functionality in mind.

Our partner, Cure Rare Disease, is a leading organization fighting to find a cure for DMD. Watch this short video to learn more about their organization. To get involved, visit CureRareDisease.org