What is McCune-Albright syndrome?

McCune-Albright condition is an extremely rare disease that affects the bones, the skin and the endocrine system. Children with McCune-Albright condition have weakened bones that break easily. The disorder is present at birth, but symptoms may not appear until later in childhood. McCune-Albright affects boys and girls equally.

Signs and symptoms

Symptoms of McCune-Albright syndrome range in severity. Some children are diagnosed in infancy while others may not show symptoms until later in childhood.

McCune-Albright syndrome includes at least two of the following three features:

• Fibrous dysplasia. This disease destroys bone and replaces it with soft, stringy tissue that is more fragile than bone and prone to break. Fibrous dysplasia is confined to one side of the body and can lead to uneven growth, deformities and limping. Scoliosis (abnormal curvature of the spine) may also occur.
• Light brown patches of skin. Called café-au-lait spots, these have irregular borders and may be present at birth. They appear on one side of the body.
• Early puberty. This is more common in girls than in boys. Girls as young as 2 years old may have their menstrual period and may develop breasts because of excess estrogen. Children who reach puberty early tend to have short stature as adults.

McCune-Albright syndrome may also affect the thyroid. The thyroid gland, located at the base of the neck, may become enlarged. About half of people with the syndrome produce excess thyroid. Symptoms include a fast heart rate, high blood pressure, weight loss, tremors and sweating.

The pituitary gland may produce too much growth hormone. This results in a condition called acromegaly, characterized by large hands and feet, arthritis, and coarse facial features.

Cause

McCune-Albright syndrome is a genetic disorder caused by a random mutation of the gene, GNAS1. The syndrome is not inherited. Rather, the gene mutation takes place after conception and not all of the copies of the GNAS1 gene have the abnormality. The severity of the disease depends on the number of cells in the body that have the faulty gene.

Testing and diagnosis

McCune-Albright may be suspected at birth if the baby is born with café-au-lait spots. Otherwise, it may not be diagnosed until puberty develops early in childhood or bone deformities become obvious.  

Your child’s doctor will conduct a complete physical examination to check for café-au-lait spots and other symptoms of McCune-Albright syndrome. An X-ray and bone scan will reveal whether fibrous dysplasia is present and blood tests will show whether certain hormone levels are elevated.

Treatment

Treatment will be directed toward your child’s specific symptoms. Because McCune-Albright syndrome is a complex disorder, your child’s treatment team may include pediatricians, orthopedists, endocrinologists and counselors. Depending on the symptoms, treatment may include:

• Drugs that inhibit bone resorption
• Surgery to correct deformities and treat complications such as scoliosis
• Exercises to strengthen the muscles surrounding fibrous dysplasia lesions
• Hormone therapy to manage precocious puberty
• Drug therapy and/or surgery to treat hyperthyroidism