Hemifacial Microsomia

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Hemifacial microsomia

Definition

Hemifacial microsomia is a general diagnosis used to describe facial birth defects of varying severity that may involve certain differences in the eyes, ears, facial bones, mouth, neck, or spine. These defects usually affect only one side of the face, with that side of the face appearing smaller than the other side.

Description

Individuals with hemifacial microsomia have physical differences that are present at birth (congenital). These abnormalities are typically limited to the head and bones of the spinal column (vertebrae) and may be severe or mild. In some cases, the changes are seen on both sides of the face (bilateral). In other cases, they are limited to one side of the face (unilateral).

Different terms may be used for this pattern of differences. Hemifacial microsomia may also be called Goldenhar syndrome, facioauriculovertebral sequence, or oculoauriculovertebral spectrum. This final name describes the common birth defects seen in persons with hemifacial microsomia. The term oculo represents the eye, and the term auriculo represents the ear. Finally, the term vertebral stands for the physical problems present in the vertebrae.

Genetic profile

Hemifacial microsomia is caused by a disruption of normal facial development. A baby's face forms very early, normally between the eighth and twelfth weeks of pregnancy. Normal facial development depends on many different tissues growing together. When the movement and development of these tissues is disrupted, the face may have abnormal openings, underdevelopment, and/or excess skin. In hemifacial microsomia, some unknown event disrupts normal development of the first and second branchial arches, the embryonic structures that later develop into the sides of face, the jaw, and the neck.

The possible causes for the embryonic disruption that leads to hemifacial microsomia are unknown. There are most likely many different factors that may lead to the abnormal development of the facial tissues. In some cases, these factors may be environmental. For example, there are certain medications a woman can take while pregnant that can cause the baby to have the symptoms of hemifacial microsomia. However, in the vast majority of cases, hemifacial microsomia is not caused by something taken during pregnancy.

In other cases, normal development of the facial tissues may be disrupted by genetic factors. The exact genetic factors are unknown. Unlike some other syndromes, there has not been a gene identified that, if changed, causes hemifacial microsomia. Studies in a few persons with hemifacial microsomia point to a possible causative genetic difference located on the long arm of chromosome 14; however, as of early 2005, this finding requires further study and characterization.

A few families in which hemifacial microsomia occurs show an autosomal recessive inheritance pattern, while other families show autosomal dominant pattern of inheritance. However, most cases of hemifacial microsomia are not inherited, meaning that it does not normally run in families.

Hemifacial microsomia typically occurs randomly. Doctors are often unable to explain why it developed. Since it is sporadic in nature, if a child is diagnosed with hemifacial microsomia, the risk for the parents to have another child with hemifacial microsomia is low. In rare cases, one parent may have some of the physical symptoms of hemifacial microsomia. If this is the case, then the risk to have a child with the disorder may be higher.

Demographics

Hemifacial microsomia occurs once in every 3,000–5,000 live births. Males are affected more frequently than females. This syndrome is seen in all ethnic groups and cultures.

Signs and symptoms

The symptoms associated with hemifacial microsomia are highly variable. Some individuals with hemifacial microsomia have many severe abnormalities, while other individuals have few minor birth defects.

The abnormalities seen in hemifacial microsomia are typically limited to the face and vertebrae. Thirty percent of patients have bilateral facial abnormalities. In these patients, the right side is usually affected more severely. The commonly observed facial asymmetry seen in persons with hemifacial microsomia is caused by hypoplasia (underdevelopment) of the bones of the face. These bones are called the mandible and the maxilla. In addition to the bones of the face, the muscles of the face can also be underdeveloped. Cleft lip and cleft palate are another facial difference associated with hemifacial microsomia. Cleft lip is an abnormal split or opening in the lip that can extend towards the nose or towards the cheek. Cleft palate is an opening in the roof of the mouth. Individuals with hemifacial microsomia can also have wide mouth (macrostomia).

Birth defects of the eye are common in hemifacial microsomia. Cysts on the eyeball (epibulbar dermoids) are common, as is micropthalmia (small eye). Some individuals with Goldenhar syndrome have a notch of tissue missing from the upper eyelid (coloboma). Strabismus (crossing of the eyes) is also prevalent.

Abnormal development of the ears is another characteristic of the hemifacial microsomia spectrum. The ears may be smaller than normal (microtia), or absent (anotia). Ear tags (excess pieces of skin) may be seen on the cheek next to the ear and may extend to the corner of the mouth. The shape of the ears may also be unusual. Hearing loss is common in individuals with hemifacial microsomia.

The vertebral problems seen in many persons with hemifacial microsomia result from improper development of the vertebrae. Vertebrae can be incompletely developed (hemivertebrae), absent, or fused. Ribs can also be abnormal. Approximately 50% of individuals with hemifacial microsomia will have curvature of the spine (scoliosis ).

Other differences outside of the face and vertebra can occasionally be seen in hemifacial microsomia. Approximately 15% of individuals with hemifacial microsomia have developmental delay or mental retardation. The likelihood for mental retardation increases if the individual has microophthalmia. Heart defects and kidney defects can also occur. Arm defects, though rare, may also occur.

Diagnosis

There is not a genetic test that can diagnose hemifacial microsomia. The diagnosis is made when an individual has the common symptoms associated with the condition. The diagnosis is made by a physician based on the observed physical features.

Treatment and management

Once a child is diagnosed with hemifacial microsomia, additional tests should be performed. A hearing evaluation is necessary to determine if there is hearing loss. If hearing loss is evident, the child should be referred to a hearing specialist. Speech therapy may also be helpful. X rays of the spine are recommended to determine if there are vertebral problems. Individuals with hemifacial microsomia may be followed regularly to check for scoliosis. Renal ultrasounds and ultrasounds of the heart may also be recommended, due to the increased risk for birth defects in these areas. A doctor would make this recommendation. Finally, individuals with hemifacial microsomia should be evaluated by an eye doctor (ophthalmologist).

Surgery may be required to correct the birth defects seen in hemifacial microsomia. Surgery to correct the facial birth defects can improve appearance and function.

Prognosis

The prognosis for individuals with hemifacial microsomia is very good. These individuals typically have a normal lifespan and normal intelligence.

Resources

BOOKS

Gorlin, Robert J., Michael M. Cohen, and Raoul C. M. Hennekam. "Branchial Arch and Oral-Acral Disorders." In Syndromes of the Head and Neck, 4th ed. New York: Oxford University Press, 2001.

Jones, Kenneth Lyons. "Oculo-Auriculo-Vertebral Spectrum." In Smith's Recognizable Patterns of Human Malformation. Philadelphia: W. B. Sanders, 1997.

PERIODICALS

Schaefer, G. Bradley, Ann Olney, and Peg Kolodziej. "Oculoauriculo-vertebral Spectrum." ENT—Ear, Nose & Throat Journal 77 (1998): 17–18.

ORGANIZATIONS

Alliance of Genetic Support Groups. 4301 Connecticut Ave. NW, Suite 404, Washington, DC 20008. (202) 966-5557. Fax: (202) 966-8553. (April 4, 2005.) <http://www.geneticalliance.org>.

Goldenhar Parent Support Network. 3619 Chicago Ave., Minneapolis, MN 55407-2603. (612) 823-3529.

Goldenhar Syndrome Support Network. 9325 163 St., Edmonton, ALB T5R 2P4. Canada. (April 4, 2005.) <http://www.goldenharsyndrome.org>.

National Organization for Rare Disorders (NORD). PO Box 8923, New Fairfield, CT 06812-8923. (203) 746-6518 or (800) 999-6673. Fax: (203) 746-6481. (April 4, 2005.) <http://www.rarediseases.org>.