Melorheostosis

What is melorheostosis?

Melorheostosis (meh-lo-ree-ohs-TOE-sis) is a rare bone disorder. It causes new bone tissue to grow on your existing outer bone layers (cortical bones). This tissue growth leads to an overly thick or wide bone. It usually affects only one of your arms or legs, but it can happen in other bones. Symptoms typically appear during childhood or adolescence.

When this new bone tissue grows, it has a characteristic look on an X-ray: Doctors describe it as looking like dripping or flowing candle wax.

Melorheostosis is a very rare type of skeletal dysplasia. Another name for melorheostosis is Leri disease.

Where does the name melorheostosis come from?

Melorheostosis comes from three Greek words:

• Melos means limb.
• Rheos means flow.
• Ostosis means bone formation.

How does melorheostosis affect my body?

If you or your child has melorheostosis, unusually thick or wide bones may limit movement. People with melorheostosis may also have a joint deformity (contracture) or pain. As bone tissue grows, you may also notice skin changes, including skin thickening or shininess.

Melorheostosis doesn’t spread to other bones, but it can worsen over time.

How common is melorheostosis?

Melorheostosis is very rare. Experts estimate that it affects about 1 in 1 million people worldwide.

What causes melorheostosis?

In about 1 in 2 cases, melorheostosis occurs because of a change (mutation) in the MAP2K1 gene. The MAP2K1 gene makes a specific protein that controls how bone cells grow. This gene change happens randomly (sporadically). It isn’t passed down from your parents.

About half of people with melorheostosis don’t have a MAP2K1 gene mutation. In these cases, healthcare providers don’t know what causes the condition.

What are the symptoms of melorheostosis?

About 1 in 2 people with melorheostosis experience symptoms by age 20. Usually, symptoms develop in childhood, possibly even in the first few days of life. They may get more severe over time.

Symptoms usually only affect the arm or leg. Less commonly, you or your child might have symptoms that affect the pelvis, breastbone (sternum) or ribs, such as:

• Chronic pain.
• Hardened or shiny skin.
• Limb swelling due to fluid buildup (edema or lymphedema).
• Limited range of motion.
• Muscle wasting (atrophy).
• Uneven arm or leg lengths.

How is melorheostosis diagnosed?

Healthcare providers use imaging tests to diagnose melorheostosis, including:

• Bone scans use injections of a small dose of radioactive material and imaging scans.
• X-rays use safe, low doses of radiation to view bones and soft tissues. If you have melorheostosis, your bones look like they are “dripping wax” on an X-ray.

Healthcare providers may also recommend genetic testing. Genetic tests are blood tests to look for the gene mutation that causes melorheostosis.

How is melorheostosis treated?

There’s no cure for melorheostosis, but treatment can help you or your child manage symptoms. Providers may prescribe treatments to manage pain and improve function, such as:

• Physical therapy to increase strength and range of motion.
• Occupational therapy to improve fine motor skills and help you or your child complete daily activities such as bathing or getting dressed.
• Medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce pain or bisphosphonates to strengthen bones.
• Surgery to remove excess bone growth or reshape bones.

How can I prevent melorheostosis?

Because melorheostosis happens randomly, there’s no way to prevent it.

What are the long-term effects of melorheostosis?

Melorheostosis isn’t cancerous, and it doesn’t affect your life expectancy. But it can limit your function and movements. You may deal with joint pain or swelling. The right treatment plan can help people with melorheostosis live a higher quality of life.

What else should I ask my healthcare provider?

If you or your child has symptoms or received a diagnosis of melorheostosis, ask your healthcare provider:

• What are the early symptoms of melorheostosis?
• What tests do I need to diagnose melorheostosis?
• What are the treatment options for melorheostosis?
• What may happen if I choose not to treat melorheostosis?
• How can I increase my quality of life with melorheostosis?

What conditions have similar symptoms to melorheostosis?

Several conditions cause symptoms similar to melorheostosis. Your healthcare provider may rule out these conditions during diagnosis, including:

• Buschke-Ollendorff syndrome.
• Desmoid tumor.
• Hemangioma.
• Osteopathia.
• Osteopoikilosis.
• Scleroderma.

A note from Cleveland Clinic

Melorheostosis is a rare bone disorder. It causes new bone tissue to grow on top of existing bone tissue. It usually affects only one limb. It doesn’t spread from bone to bone, but it can worsen over time. If you have melorheostosis, your treatment plan may include medication, physical therapy, occupational therapy or surgery. These treatments can help you live a higher quality of life with melorheostosis.