Many people have heard of muscular dystrophy, but they may not know that this term includes more than 30 different conditions. Bethlem myopathy is one of them. It belongs to a group of conditions called collagen VI-related dystrophies (COL6-RDs). These are caused by changes in genes that affect the collagen type VI protein.

In Bethlem myopathy, these gene changes lead to muscle weakness and joint stiffness that slowly get worse over time. Bethlem myopathy is the mildest form of COL6-RD. Symptoms can start at any age, but they most often begin in childhood.

In this article, we discuss Bethlem myopathy, what symptoms it causes, how it affects daily life, and what treatment and management options are available.

What Is Bethlem Myopathy?

Bethlem myopathy is a rare disease that’s estimated to affect fewer than 5,000 people in the U.S. It’s a form of muscular dystrophy, and it’s also a neuromuscular disorder, meaning it affects both the muscles and the nerves that control them. Bethlem is the mildest of three phenotypes (types) of COL6-RD. The most severe type is called Ullrich congenital muscular dystrophy.

Bethlem myopathy is a congenital condition, which means a person is born with it. Some signs of Bethlem myopathy may appear before birth, such as reduced movement in the womb. However, symptoms may also appear anytime from birth to adulthood. In many cases, symptoms of muscle weakness first appear in early childhood.

Children with symptoms of Bethlem myopathy may take longer to reach motor milestones like sitting up or walking. Progressive muscle weakness gets worse slowly over time. Some people with Bethlem myopathy may need mobility aids, such as a cane or wheelchair, especially as they reach middle age or older.

What Causes Bethlem Myopathy?

Like other types of muscular dystrophy, Bethlem myopathy is a genetic (inherited) disorder. It happens because of mutations in one of the three genes — COL6A1, COL6A2, and COL6A3 — that help make a protein called collagen type VI.

Everyone inherits one copy of the collagen VI gene (COL6) from each parent. In most cases, a child with Bethlem myopathy has a mutation in just one copy of a COL6 gene. This inheritance pattern is called autosomal dominant, meaning the mutated version of the gene from one parent is enough to cause the condition.

In rare cases, a child inherits two mutated copies of COL6 genes — one from each parent. This is called autosomal recessive inheritance.

Collagen VI proteins are important for keeping muscle cells strong and healthy. If these proteins are missing or don’t work properly, they can’t provide the support that muscles need. As a result, muscle cells weaken and get damaged over time. This damage and weakness lead to the symptoms of Bethlem myopathy.

Symptoms of Bethlem Myopathy

Symptoms of Bethlem myopathy often begin in childhood but can also appear later in life. The speed at which symptoms progress and their severity are different from person to person. Some people with Bethlem myopathy may only have some of these symptoms.

Muscle Weakness

Muscle weakness in Bethlem myopathy tends to get worse gradually over time. Signs of muscle weakness can appear at different stages:

• Before birth — Reduced movement of the fetus
• After birth — Hypotonia (low muscle tone)
• Early childhood — Delayed milestones, such as sitting up or walking later than usual
• Adulthood — Weakness in proximal muscles (muscles near the body’s center), such as the shoulders and hips, which can limit mobility

Some babies may also have stiff neck muscles, a condition known as torticollis.

Later in life, adults with Bethlem myopathy often have trouble standing up from a seated position. Reduced muscle strength can also make it difficult for people with the condition to climb stairs or lift their arms above their head. By age 50, more than two-thirds of people with Bethlem myopathy use a mobility aid, such as a cane or walker, when outside. Many can still move around indoors without help.

Joint Stiffness

Another common symptom of Bethlem myopathy is joint stiffness. This happens because of joint contractures, which are caused by tight tendons in the muscles. This stiffness makes it hard to move, and especially to straighten, the joints. Joint contractures usually appear in adulthood and tend to affect the wrists, elbows, fingers, and Achilles tendons (in the back of the ankle).

In contrast, children with Bethlem myopathy may have loose or overly flexible joints. This joint laxity can lead to “W-sitting,” a position where the legs are bent out to the sides in the shape of a W.

While joint stiffness limits movement, contractures don’t usually get worse in adulthood. Some people may also develop stiffness in the spine. In some cases, this can lead to scoliosis (a curve in the spine).

Breathing Problems

Weak respiratory muscles may also lead to trouble breathing in people with Bethlem myopathy. These issues may happen in children even if their movement is still fairly normal. During sleep, breathing may change or be shallow. Signs of nighttime breathing issues include:

• Morning headaches
• Daytime sleepiness
• Unexplained weight loss
• Loss of appetite

Children with Bethlem myopathy should be checked regularly for breathing problems. If your child has signs of nighttime breathing issues, their doctor may recommend a sleep study to monitor how the child breathes while sleeping.

Skin Issues

Because collagen VI is also found on the skin, some people with Bethlem myopathy have certain skin abnormalities. These can include:

• Bumpy or rough skin on the arms and legs (called hyperkeratosis pilaris)
• Slow healing of cuts or skin injuries, which can result in scarring
• Thick, raised scars (called keloids) where skin has been injured or damaged

Due to slow healing and a higher risk of scarring, it’s important to prevent skin injuries as much as possible. Scars may also form after surgery or from pressure sores, so protecting the skin is a key part of care.

Treating and Managing Bethlem Myopathy

If you or a loved one has symptoms of Bethlem myopathy, getting diagnosed is the first step. A neurologist can make a diagnosis of Bethlem myopathy using a combination of physical exams, family history, and testing. These tests may include:

• Genetic testing
• Muscle MRI or other imaging
• Muscle biopsy

Bethlem myopathy symptoms tend to get worse over time, more often during adulthood than in childhood. The condition doesn’t usually shorten life expectancy. However, joint stiffness, a decline in mobility, and other symptoms can affect quality of life. Adults may find it harder to stand, climb stairs, or do daily tasks like brushing their hair. Many older adults with Bethlem myopathy use mobility aids to get around outdoors.

Treatment for Bethlem myopathy focuses on managing symptoms. Your neurologist and a team of healthcare professionals may suggest different treatments to best meet your needs.

Physical Therapy

Physical therapy plays a key role in managing Bethlem myopathy symptoms. It uses specific exercises, movements, and manual therapies to help reduce symptoms. This intervention can support mobility, strength, and breathing. Physical therapy may also help slow the progression of joint stiffness.

A physical therapist can help you design an exercise plan tailored to your needs. Depending on your abilities, they may suggest moderate aerobic exercises, such as walking or swimming. These exercises not only help manage your symptoms, but also support a healthy weight and heart. A physical therapist can also help you choose the right mobility aids.

Orthopedic Support

In addition to exercise, it’s important to take care of your joints, bones, and muscles when living with Bethlem myopathy. To do this, an orthopedist may recommend orthotic devices — such as braces or splints — to support weakened muscles and joints. These devices may help with Bethlem myopathy symptoms such as contractures and scoliosis.

If you have severe contractures or scoliosis, your provider may recommend surgery. Achilles tendon surgery can help improve issues with standing and walking. Spinal surgery might be an option for correcting scoliosis. Your healthcare team will work with you to choose the treatment plan that best fits your needs.

Talk With Others Who Understand

On myMDteam, the social network for people with muscular dystrophy and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with muscular dystrophy.

Do you have Bethlem myopathy? Share your experience in the comments below or start a conversation by posting on your Activities page.