Hemifacial microsomia

What causes hemifacial microsomia?

For most people with hemifacial microsomia, the cause is unknown. It is believed that something occurs in the early stages of development, such as a disturbance of the blood supply to the first and second branchial arches in the first 6 to 8 weeks of pregnancy.

Studies have suggested multiple possible risk factors for hemifacial microsomia. Environmental risk factors include the use of medications during pregnancy such as Accutane, pseudoephedrine, aspirin, or ibuprofen. Other environmental factors include second trimester bleeding, maternal diabetes, being pregnant with multiples, or the use of assisted reproductive technology. A genetic cause is found in some families, such as a chromosome disorder or a genetic syndrome.

Some possible explanations when the cause of hemifacial microsomia is unknown include a very small chromosome deletion or duplication that is not detected, a mutation in an unknown gene, or changes in multiple genes associated with development of the face. It is also possible that a combination of genetic changes and environmental risk factors could cause hemifacial microsomia.

Last updated on 05-01-20

What causes hemifacial microsomia?

The underlying cause of hemifacial microsomia remains unknown. However, most researchers agree that something occurs in the early stages of development, such as a disturbance of the blood supply to the first and second branchial arches in the first 6 to 8 weeks of pregnancy.[ Tissue layers in the six pairs of pharyngeal arches give rise to the muscles, arteries, nerves, and cartilage of the face and neck. Specifically, the first and second pharyngeal arches develop into the lower jaw, the nerves and muscles used for chewing and facial expression, the external ear, and the bones of the middle ear. Interference with the normal development of these structures can result in the abnormalities seen in hemifacial microsomia. It is not known why certain disruptions to development affect the first and second pharyngeal arches in particular. Researchers suggest that these structures may develop together in such a way that they respond as a unit to these disruptions.

There appear to be several factors that can disrupt the normal development of the first and second pharyngeal arches and lead to hemifacial microsomia. Some individuals with this condition have chromosomal abnormalities such as deletions or duplications of genetic material; these individuals often have additional developmental problems or malformations. Occasionally, hemifacial microsomia occurs in multiple members of a family in a pattern that suggests inheritance of a causative gene mutation, but the gene or genes involved are unknown. In other families, individuals seem to inherit a predisposition to the disorder. The risk of hemifacial microsomia can also be increased by environmental factors, such as certain drugs taken by the mother during pregnancy. In most affected individuals, the cause of the disorder is unknown.

Last updated on 05-01-20

Is hemifacial microsomia inherited?

Hemifacial microsomia most often occurs in a single individual in a family and is not inherited. If the condition is caused by a chromosomal abnormality, it may be inherited from one affected parent or it may result from a new abnormality in the chromosome and occur in people with no history of the disorder in their family. In a very small number of cases, hemifacial microsomia is inherited in an autosomal dominant pattern, which means one copy of an altered gene in each cell is sufficient to cause the disorder. In rare cases, the condition is inherited in an autosomal recessive pattern, which means both copies of a gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. The gene or genes involved in hemifacial microsomia are unknown.

In some affected families, people seem to inherit an increased risk of developing hemifacial microsomia, not the condition itself. In these cases, some combination of genetic changes and environmental factors may be involved.

Last updated on 05-01-20

What types of specialists are involved in the treatment of hemifacial microsomia?

Ideally, people with hemifacial microsomia should be managed by a team of specialists that work together. A qualified, craniofacial medical team can be found at a craniofacial center. Depending on the features and severity in the affected person, specialists involved in treatment may include:

  • audiologist
  • dietitian
  • ophthalmologist (eye doctor)
  • oral and maxillofacial surgeon (face, mouth and jaw surgeon)
  • orthodontist to treat crowding of teeth
  • orthopedist to assess spine issues
  • otolaryngologist for any nose or throat issues
  • dentist or pediatric dentist to assess dental health
  • plastic and reconstructive surgeon
  • speech pathologist to address speech problems
  • psychologist or social worker to address social, emotional or psychological issues.

Other types of specialists may also be needed depending on the features present in each person.

Last updated on 05-01-20

How might hemifacial microsomia be treated?

Treatment of hemifacial microsomia varies depending on the features present and the severity in each affected person. Various types of surgeries may be needed in many cases.

Some children need breathing support or a tracheostomy soon after birth if the jaw is severely affected. However in most cases, airway problems can be managed without surgery. Those with a jaw deformity and/or clefts may have feeding problems and may need supplemental feedings through a nasogastric tube to support growth and weight gain. Babies born with cleft lip or palate can have surgical repairs done during the first year. Cleft lip repair is typically performed when the child is 3-6 months old, while cleft palate surgery is generally performed when the child is about a year old. A lateral facial cleft, one of the most severe abnormalities associated with the condition, also requires reconstruction in stages.

If eye closure is incomplete due to eyelid abnormalities or facial paralysis is present, a child may need eye protection or surgery. Surgery may also be used for eyelid differences to reposition the lower lids and corners of the eyes. Some children with abnormally shaped or missing ears may choose to have a series of reconstructive surgeries to make the ear appear more normal. Children with skin, cheek and other soft tissue deficiencies may need augmentation procedures such as fat grafting or tissue transfer. Severe bone abnormalities may require surgery as well.

Because multiple body systems may be involved in hemifacial microsomia, affected people should continually be monitored for complications.

Last updated on 05-01-20

Name: National Association of the Deaf 8630 Fenton Street Suite 820
Silver Spring, MD, 20910 , United States
Phone: +1-301-587-1788 TTY: +1-301-587-1789 Fax : +1-301-587-1791 Email: NADinfo@nad.org Url: https://www.nad.org/
Name: About Face International 51 Wolseley Street Toronto, ON M5T 1A4
Phone: +1-416-597-2229 Toll Free: 1-800-665-3223 Fax : +1-416-597-8494 Email: info@aboutface.ca Url: https://www.aboutface.ca/
Name: FACES: The National Craniofacial Association PO Box 11082
Chattanooga, TN, 37401, United States
Phone: 423-266-1632 Toll Free: 800-332-2373 Email: faces@faces-cranio.org Url: http://www.faces-cranio.org/
Name: Children's Craniofacial Association 13140 Coit Road Suite 517
Dallas, TX, 75240 , United States
Phone: +1-214-570-9099 Toll Free: 1-800-535-3643 Fax : +1-214-570-8811 Email: contactCCA@ccakids.com Url: https://ccakids.org/
Name: Ameriface PO Box 751112
Las Vegas, NV, 89136, United States
Phone: 702-769-9264 Toll Free: 888-486-1209 Email: info@ameriface.org Url: http://www.ameriface.org
Name: American Society for Deaf Children (ASDC) PO Box 23
Woodbine, MD, 21797, United States
Toll Free: 1-800-942-2732 Email: info@deafchildren.org Url: http://deafchildren.org/

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