What Is Hemihyperplasia?

Medically Reviewed by Dan Brennan, MD on February 20, 2024
Written by Victoria Hamilton
3 min read

Hemihyperplasia, also known as hemihypertrophy or overgrowth syndrome, is when one side of the body grows faster than the other side as a result of bone or soft tissue that doesn’t stop growing. It can look different for everyone affected, and it’s common in children.

Hemihyperplasia can affect one part of the body or multiple areas. The syndrome can affect bones, skin, muscle, fat, and nerves. Places you can develop hemihyperplasia include:

  • Arms
  • Face
  • Legs
  • Tongue
  • Jaw
  • Teeth
  • Ears

One of your legs might be longer and thicker than your other leg, an entire side of your body might appear larger than the other, or other parts of your body will look asymmetrical.

This condition can show up by itself or present as one symptom of certain genetic syndromes. It’s possible to diagnose hemihyperplasia at birth, but it can show up anytime during childhood. Growth patterns are irregular, so there may be times when affected areas grow quickly and times when growth is slow.

Hemihyperplasia is usually caused by another medical condition, including:

  • Beckwith-Wiedmann syndrome: A disorder primarily known for the overgrowth of organ systems. Common symptoms include an enlarged tongue, kidney issues, facial and heart abnormalities, and advanced bone age.
  • Klippel-Trenaunay syndrome: A rare condition affecting the blood and lymph vessels. Common symptoms include harmless growths of blood vessels on the skin, varicose veins, fused or extra toes and fingers, and internal bleeding.
  • Proteus syndrome: A disorder that causes uneven overgrowth in a random, patchy pattern. Common symptoms include brain overgrowth and a dark, rough scar on the feet or hands.
  • Neurofibromatosis Type I: A genetic condition that results in non-cancerous tumors growing alongside your nerves. Common symptoms include brown birthmarks anywhere on your body, soft, benign tumors on or below your skin, groups of freckles in odd places like your armpits or groin, and issues with your bones, eyes, and nervous system. 
  • Russel-Silver syndrome: an uncommon birth complication that keeps the fetus and newborn child from growing properly. Common symptoms include a triangular-shaped face, difficulty eating, a bent fifth finger, and short stature.
  • Sotos syndrome: A rare genetic disorder that causes fast physical growth in children. Common symptoms include large heads, hands, and feet, as well as eyes that slant downwards and delayed motor, mental, and social growth.

Hemihyperplasia symptoms include visible inconsistencies in body part growth. For example, a child with hemihyperplasia might only show subtle differences in size between the two sides of their face. With time, overgrowth will be more noticeable. It could interfere with daily activities like eating, chewing, and breathing.

There are no tests developed specifically to diagnose hemihyperplasia. The condition is usually obvious from the visible differences in growth in the body. Your doctor may want to test you for other medical conditions.

Your doctor might also suggest genetic testing to look for signs of issues that are more common in people with hemihyperplasia. For example, people with this syndrome are more likely to get cancer in certain organs. Frequent ultrasounds and blood testing to check for the presence of tumors is highly recommended.

If you think you have hemihyperplasia, consult your doctor. They can perform clinical examinations, CT scans, and MRIs to accurately diagnose your condition.

While overgrowth syndrome has no cure, there are options for hemihyperplasia treatment to improve lost function or appearance-related concerns. There are a variety of procedures you can get to make sure your nerves and muscles keep functioning as they should. If you want to address your hemihyperplasia, you can consider: