Muscular dystrophy is a group of conditions caused by genetic mutations — changes in your DNA — that cause muscle weakness. Most people with muscular dystrophy inherit the condition from one or both parents. Sometimes, a random genetic mutation can cause muscular dystrophy, even if there’s no family history.

You can’t catch muscular dystrophy from another person or get it from an injury or illness. This article will review how muscular dystrophy is inherited — that is, how it can be passed from parents to their children through genes.

How Does Muscular Dystrophy Affect Muscles?

The genetic changes that occur in muscular dystrophy affect the strength of your muscle fibers. Each muscle fiber is surrounded by an outer layer of proteins (called a membrane) and attached to other body structures with connective tissue.

In muscular dystrophy, genetic changes can affect proteins involved in making the membrane that surrounds muscle fibers or connective tissue. When these structures are damaged or don’t work as well, the muscle fibers they protect can also become damaged. This can lead to muscle damage and muscle weakness that gets worse over time.

Changes in the genes that make muscle proteins can cause different types of muscular dystrophy.

For example, in Duchenne muscular dystrophy and Becker muscular dystrophy, genetic mutations to the dystrophin gene result in an abnormal membrane protein called dystrophin. Dystrophin is a protein in the membrane that surrounds muscle fibers. Without dystrophin protein, muscle fibers can become damaged and weaken over time. In myotonic dystrophy, changes in certain genes cause muscle proteins to not work properly.

How Is Muscular Dystrophy Inherited?

Muscular dystrophy is passed down from parent to child in most cases. The way muscular dystrophy is inherited depends on what part of your DNA the mutation is found in.

There are three ways that muscular dystrophy can be inherited. We’ll discuss how each works below.

X-Linked Inheritance

Conditions with an X-linked inheritance have a genetic mutation found on the X chromosome.

The X chromosome is one of two sex chromosomes that help determine biological sex. In physiological circumstances, females have two X chromosomes, one inherited from each parent. Males have one X chromosome from their mother and one Y chromosome from their father.

Conditions with X-linked recessive inheritance are more common in males than females because males only have one X chromosome. If a woman has one copy of a muscular dystrophy gene on the X chromosome, each son has a 50 percent chance of inheriting the mutation, according to the Muscular Dystrophy Association (MDA). Each daughter also has a 50 percent chance of inheriting one copy of the mutation and becoming a carrier, per the MDA. Because a daughter will have another X chromosome from the father, there may not be any symptoms of the disease.

Carriers usually don’t have any symptoms but can pass the disease on to future children. The MDA notes that in rare cases, a female carrier may have some symptoms, called a manifesting carrier.

Types of muscular dystrophy that are more common in males than females have an X-linked inheritance pattern. These include:

• Becker muscular dystrophy
• Duchenne muscular dystrophy
• Emery-Dreifuss muscular dystrophy

Autosomal Dominant Inheritance

When a condition follows an autosomal dominant inheritance pattern, it takes just one copy of a genetic mutation from one parent to cause the disease. Conditions with autosomal dominant inheritance can be passed down from a parent with the disease. If a parent has the disease, each child has a 50 percent chance of also developing it.

Autosomal refers to the fact that the gene isn’t found on a sex chromosome. Because the mutation isn’t on a sex chromosome, it can affect males and females equally. Types of muscular dystrophy that affect males and females equally may have this type of inheritance pattern, according to the MDA.

Examples of types of muscular dystrophy with an autosomal dominant inheritance pattern include:

• Distal muscular dystrophy
• Emery-Dreifuss muscular dystrophy
• Facioscapulohumeral muscular dystrophy
• Limb-girdle muscular dystrophy
• Myotonic dystrophy
• Oculopharyngeal muscular dystrophy

All of the above except for myotonic dystrophy and facioscapulohumeral muscular dystrophy can also be inherited through an autosomal recessive pattern of inheritance.

Autosomal Recessive Inheritance

Conditions with autosomal recessive inheritance require two copies of a genetic mutation — one from each parent — to develop the disease. To pass on a condition with this type of inheritance pattern, both parents must have the genetic mutation. The parents usually don’t have any symptoms of the disease.

The MDA has found that both males and females can be affected by a condition with an autosomal recessive pattern of inheritance because it’s not linked to a sex chromosome.

Some types of muscular dystrophy can be inherited through an autosomal recessive pattern, including:

• Distal muscular dystrophy
• Emery-Dreifuss muscular dystrophy
• Limb-girdle muscular dystrophy
• Oculopharyngeal muscular dystrophy

Can You Have Muscular Dystrophy Without a Family History?

Most people with muscular dystrophy have a family history of the disease. However, it’s also possible to be the first person in your family with the disease. There are two ways this can happen.

The first way is if there’s a carrier in the family. This can occur with forms of muscular dystrophy that are inherited through an X-linked or autosomal recessive pattern. Family members who carry a copy of the genetic mutation may not realize they’re carriers until someone else in the family develops the disease. If the condition is X-linked, it’s possible no males with the condition were previously born, or it was unknown what disease they had.

The other way to develop muscular dystrophy without a family history is from a new genetic mutation. Genetic mutations can happen randomly when cells divide. If a genetic mutation develops in a gene associated with muscular dystrophy, it can cause the disease.

A new mutation that causes muscular dystrophy can occur in two ways — in the womb during development or in the egg or sperm cells of a parent. Once a genetic mutation occurs in one person, it can be passed down to future generations.

Genetic Testing for Muscular Dystrophy

Genetic testing involves taking a sample of genetic material to check for mutations associated with muscular dystrophy. It can be used to diagnose muscular dystrophy or tell if someone is a carrier. Genetic testing can also help determine which treatments may work.

People with relatives who have been diagnosed with muscular dystrophy may be tested to check if they are carriers. A genetic counselor can discuss with you the need for testing and help you understand the results of a genetic test for muscular dystrophy. Talk to your health care provider to find out if you or your child is eligible for genetic testing.

Find Your Team

On myMDteam, the site for people with muscular dystrophy and their loved ones, people come together to gain a new understanding of muscular dystrophy and share their stories with others who understand life with the condition.

Have you or a family member been diagnosed with muscular dystrophy? If so, has genetic testing helped you understand the condition better? Share your experiences in the comments below or by posting to your Activities page.