Symptoms & Causes of Hemifacial Microsomia

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What are The Signs Of Hemifacial Microsomia?

If your child has hemifacial microsomia, the most visible signs of the condition are underdeveloped upper and lower jaws on one side of the face. It may appear that your child's mouth slants upward toward the affected side.

Often the forehead and cheek are flattened on the affected side and one eye socket is smaller than normal.

Other signs of hemifacial microsomia include:

  • Ear abnormalities: Small nodules of excess skin around the ear, underdeveloped or absent external ear, underdeveloped or absent inner ear structures and hearing loss
  • Jaw abnormalities: A small or underdeveloped jaw, upward slanted mouth/jaw, appearance of a “crooked smile,” inability to chew
  • Facial findings: Flat cheek and/or forehead, overall facial asymmetry (unevenness), weakness of muscles and loss of sensation

What is Bilateral Hemifacial Microsomia?

Rarely, this condition can occur on both sides of the face. This is referred to as bilateral facial microsomia.

Learn more about hemifacial microsomia treatments at Boston Children’s.

What Causes Hemifacial Microsomia?

Experts do not know the exact causes of hemifacial microsomia. They believe that the condition occurs because of a disrupted process in your baby’s fetal development during the first six weeks of gestation. It is not known if environmental factors are involved.

Hemifacial microsomia is thought to be inherited in some families, because there have been some cases reported where the condition occurs more than once in a family. Researchers have not yet identified the genes involved in hemifacial microsomia.

There is nothing you (or your child’s other parent) did—or did not do—that caused the hemifacial microsomia.

Make an Appointment

For an appointment with the Cleft and Craniofacial Center, more information or to obtain a second opinion for your child, please call us at 617-355-6309 or email

International Patients

For families residing outside of the United States, please call Boston Children's International Health Services at +01-617-355-5209.

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