Bossing of the Skull

Abnormal bone growth is a common symptom for children with sickle cell disease (SCD). It usually occurs because of anemia. An enlarged forehead, called bossing of the skull or frontal bossing, is an example of an abnormal skeletal development.

Frontal bossing is a sign of many genetic, or inherited, conditions. In people with SCD, it happens when skull bones expand because of an overproduction of red blood cells.

There are no specific ways to prevent or treat frontal bossing in people with SCD. It usually does not worsen with age but may become more noticeable. The focus is instead on managing the underlying condition of anemia. Cosmetic surgery may be possible, but is not a widely accepted practice.1

What is bossing of the skull?

Skull bossing is a term that describes a bulging of the skull. It happens mostly in the frontal bones of the forehead, which is called “frontal bossing.” This is often associated with an enlarged ridge above the eyebrows.1

Skull bossing is a sign of many conditions that affect hormones, bones, or blood. The most common cause is an overproduction of growth hormones. This leads to enlarged bones in the hands, feet, jaws, and skull. Certain types of anemia can also cause skull bossing.1

Skull bossing is diagnosed by measuring the head. The cause may not be as clear. However, skull bossing usually signals a rare disorder, and other symptoms offer clues as to the underlying cause. It may be mild in infants, but it can become more noticeable as children age. It usually does not improve or worsen with age.1

Why does sickle cell disease cause bossing of the skull?

Certain types of SCD can cause bossing of the skull. It is most common in people with sickle cell beta thalassemia. People with sickle cell beta thalassemia have 1 copy of the sickle hemoglobin gene and 1 copy of a mutated hemoglobin gene that lowers hemoglobin production.2

Skull bossing happens when bone marrow in the skull expands. Bone marrow is the spongy material within bones where red blood cells are produced. Bone marrow expands when it produces more red blood cells to make up for anemia. People with SCD often experience anemia because sickle red blood cells do not circulate for as long as normal red blood cells.3,4

Abnormal bone marrow expansion causes bones to become thinner, wider, and more brittle. These bones have a higher risk of breaking.5

How is bossing of the skull prevented or treated?

There are no known ways to prevent or treat frontal bossing. Management usually focuses on treating the underlying condition or reducing symptoms. For people with SCD, this means reducing the severity of anemia.

Chronic blood transfusions are often used to manage anemia. However, multiple transfusions may cause health problems, including excess iron in the body and developing immune reactions to donor blood (alloantibodies). Blood should be transfused only when absolutely necessary, and iron chelation therapy should be given with regular blood transfusions. This is a drug that chelates (binds) iron and allows it to be excreted in urine.6

Cosmetic surgery can sometimes help treat facial deformities, including skull bossing. However, there are no treatment guidelines recommending this to improve the appearance of the skull. Talk to your doctor about what you can do if you notice that you or your child’s forehead looks overly enlarged.1,7

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Written by: Matthew Zajac | Last reviewed: January 2021