McCune-Albright syndrome is a genetic condition that affects your bones, skin and endocrine system, causing café-au-lait skin pigmentation, scar tissue forming on bones (fibrous dysplasia) and irregular function of growth-regulating glands that produce hormones. Treatment alleviates symptoms of the condition and leads to a normal life expectancy, but there isn’t a cure.
McCune-Albright syndrome (also known as fibrous dysplasia/McCune-Albright) is a genetic condition that affects your bones, skin and endocrine system (hormone-producing tissues). McCune-Albright syndrome causes scars on bone tissue (fibrous dysplasia), skin pigmentation and increased function of growth-regulating glands. The condition can be fairly mild in some, and quite severe to life-threatening in others.
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McCune-Albright syndrome can affect any child because it’s the result of a new genetic mutation. These types of mutations are unpredictable. This genetic mutation occurs shortly after conception/fertilization due to an error when cells divide and replicate.
McCune-Albright syndrome is a rare condition that occurs an estimated once out of every 100,000 to 1,000,000 births worldwide.
McCune-Albright syndrome might affect your child’s height and weight due to bone growth and endocrine system symptoms of the condition. Your child may have a specific type of birthmark on their body called café-au-lait spots. Your child may also experience early puberty as a symptom. If you notice symptoms affecting your child’s ability to thrive, contact your healthcare provider for a unique treatment plan that’s focused on alleviating your child’s symptoms.
Symptoms of McCune-Albright syndrome affect your bones, skin and endocrine system. Symptoms range in severity and affect each person diagnosed with the condition differently.
The most common symptom that affects bones is fibrous dysplasia. Fibrous dysplasia is a condition where scar tissue grows in the place of normal bone. As your body grows and develops, the areas of fibrous tissue also grow and weaken your bone, causing bone fractures or bones to grow irregularly (deformed). People diagnosed with McCune-Albright syndrome might experience mild to severe cases of fibrous dysplasia based on how many bones have affected tissue.
A less common symptom of McCune-Albright syndrome is cancerous bone lesions (tumors) as a result of fibrous dysplasia, which occurs in less than 1% of people with the condition.
Other symptoms of McCune-Albright syndrome that affect the bones include:
Babies born with McCune-Albright syndrome may have patches of skin that are a different color than the rest of the skin on their body (skin pigmentation). These patches normally take on a light brown to dark brown color and appear with uneven, jagged borders (café-au-lait spots). These spots may only show up on one side of their body. Café-au-lait spots may become more prevalent on their skin as your child becomes older.
McCune-Albright syndrome may affect a child’s endocrine system, which is a series of glands that produce hormones. This condition can cause early puberty in children, especially in children assigned female at birth, who may begin menstruating by two years of age. Early menstruation occurs because excess female sex hormones (estrogen) excrete from cysts that form in their ovaries. Children assigned male at birth might experience early puberty as well.
Nearly 50% of people diagnosed with McCune-Albright syndrome have an enlarged thyroid gland. When the thyroid gland enlarges, it produces too much of the thyroid hormone (hyperthyroidism) that causes a fast heart rate, excessive sweating, high blood pressure and weight loss.
Other endocrine system symptoms of McCune-Albright syndrome include:
A mutation of the GNAS1 gene causes McCune-Albright syndrome. The GNAS1 gene makes proteins that regulate hormone activity. The mutation causes an enzyme (adenylate cyclase), which is a type of protein, to overproduce hormones and cause symptoms of McCune-Albright syndrome.
The genetic mutation is the result of a change in DNA that happens after conception (somatic mutation) and isn’t a condition that’s passed from parents to the child. The genetic mutation is not the result of something that the parents did or did not do during pregnancy. There have been no proven cases of people with McCune-Albright syndrome having a child with the same condition. The cause of somatic mutations is unknown and research suggests they occur randomly or sporadically.
McCune-Albright syndrome is typically diagnosed during early childhood. Your healthcare provider will examine your child for physical symptoms of the condition, like endocrine irregularities, café-au-lait spots on their skin and fibrous dysplasia. Diagnosis usually triggers after signs of early puberty or irregular bone growth.
Tests that diagnose McCune-Albright syndrome include:
Treatment is unique for each person diagnosed with McCune-Albright syndrome. There isn’t a cure for the condition and treatment aims to reduce symptoms. Treatment could include:
McCune-Albright syndrome occurs because of a new genetic mutation. You can’t prevent it from happening.
Talk with your healthcare provider about genetic testing if you plan on becoming pregnant to see if you’re at risk of having a child with a genetic condition.
Prognosis is dependent on the severity of the diagnosis in your child. Most people diagnosed with McCune-Albright syndrome have a normal life expectancy. Your healthcare provider will work closely to provide the best treatment that’ll reduce your child’s symptoms and alleviate any discomfort.
Your child might be shorter than their peers because their growth plates closed too soon during early puberty, but early intervention and treatment can improve their chances of postponing puberty changes that occur too soon.
Stay up to date with your child’s developmental milestones to make sure your child is growing on track.
There is a very small risk that cancer can develop as a result of your child’s diagnosis, so it’s important to schedule regular visits with your child’s healthcare provider.
Women with McCune-Albright may have a higher chance for breast cancer that occurs at an earlier age than usual, so it’s important to discuss this with your healthcare provider and receive recommended screenings.
You should visit your healthcare provider if your child experiences symptoms of McCune-Albright syndrome, including:
If you believe your child has a bone fracture or broken bone, with symptoms of pain, swelling, difficulty moving or bearing weight on that part of their body and bruising, visit the emergency room.
A note from Cleveland Clinic
Hearing your child has a rare genetic diagnosis can be intimidating for a new parent, but early intervention and treatment are available to combat your child’s symptoms of McCune-Albright syndrome. Your healthcare provider might suggest visiting a genetic counselor who’s an expert in genetics, as well as providing emotional support to help you better understand the diagnosis and walk you through the steps you can take to support your child so they can live a healthy and fulfilling life.
Last reviewed by a Cleveland Clinic medical professional on 12/14/2021.
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