Hemifacial microsomia (HFM) is a

congenital disorder A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities c ...

that affects the development of the lower half of the face, most commonly the ears, the mouth and the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bon ...

. It usually occurs on one side of the face, but both sides are sometimes affected. If severe, it may result in difficulties in breathing due to obstruction of the

trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from th ...

—sometimes even requiring a tracheotomy. With an incidence in the range of 1:3500 to 1:4500, it is the second most common birth defect of the face, after cleft lip and cleft palate. HFM shares many similarities with

Treacher Collins syndrome Treacher Collins syndrome (TCS) is a genetic disorder characterized by deformities of the ears, eyes, cheekbones, and chin. The degree to which a person is affected, however, may vary from mild to severe. Complications may include breathing prob ...

Presentation

The clinical presentation of HFM is quite variable. The severity may depend on the extent of the area with an insufficient blood supply ''in utero'', and the gestational age of the fetus at which this occurs. In some people, the only physical manifestation may be a small and underdeveloped external ear. In more severe cases, multiple parts of the face may be affected. Some people with HFM may have sensorineural hearing loss and decreased visual acuity or even blindness. It can be thought of as a particularly severe form of HFM, in which extracranial anomalies are present to some extent. Some of the internal organs (especially the heart, kidneys, and lungs) may be underdeveloped, or in some cases even absent altogether. The affected organs are typically on the same side as the affected facial features, but bilateral involvement occurs in approximately 10% of cases. Deformities of the vertebral column such as scoliosis may also be observed. While there is no universally accepted grading scale, the OMENS scale (standing for Orbital, Mandible, Ear, Nerves and Soft tissue) was developed to help describe the heterogeneous

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological prop ...

that makes up this

sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is called ...

or syndrome.

Intellectual disability Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation, Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signif ...

is not typically seen in people with HFM. Hemifacial microsomia sometimes results in temporomandibular joint disorders.

Cause

The condition develops in the

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal develo ...

at approximately 4 weeks gestational age, when some form of vascular problem such as blood clotting leads to insufficient blood supply to the face. This can be caused by physical trauma, though there is some evidence of it being hereditary . This restricts the developmental ability of that area of the face. Currently there are no definitive reasons for the development of the condition.

Diagnosis

Classification

Figueroa and Pruzanksky classified HFM patients into three different types: * Type I : Mild hypoplasia of the ramus, and the body of the mandible is slightly affected. * Type II : The condyle and ramus are small, the head of the condyle is flattened, the glenoid fossa is absent, the condyle is hinged on a flat, often convex, infratemporal surface, the coronoid may be absent. * Type III: The ramus is reduced to a thin lamina of bone or is completely absent. There is no evidence of a

TMJ In anatomy, the temporomandibular joints (TMJ) are the two joints connecting the jawbone to the skull. It is a bilateral synovial articulation between the temporal bone of the skull above and the mandible below; it is from these bones that it ...

Treatment

Depending upon the treatment required, it is sometimes most appropriate to wait until later in life for a surgical remedy – the childhood growth of the face may highlight or increase the symptoms. When surgery is required, particularly when there is a severe disfiguration of the jaw, it is common to use a rib graft to help correct the shape. According to literature, HFM patients can be treated with various treatment options such as functional therapy with an appliance, distraction osteogenesis, or costochondral graft. The treatment is based on the type of severity for these patients. According to Pruzanksky's classification, if the patient has moderate to severe symptoms, then surgery is preferred. If patient has mild symptoms, then a functional appliance is generally used. According to Dr. Harry Pepe, a pediatrician from Hollywood, Fl, the goal of treatment in hemifacial microsomia is to elongate the deficient jaw bone to restore facial symmetry and correct the slanting bite (occlusion). Patients can also benefit from a Bone Anchored Hearing Aid (BAHA).

Terminology

The condition is also known by various other names: * Lateral facial dysplasia * First and second branchial arch syndrome * Oral-mandibular-auricular syndrome * Otomandibular dysostosis * Craniofacial microsomia

References

*
Hemifacial Microsomia
at the Tennessee Craniofacial Center. Accessed 20 January 2008. *
Hemifacial Microsomia
at the Children's Hospital and Health System of Wisconsin. Accessed 20 January 2008.

External links

GeneReviews/NCBI/NIH/UW entry on Craniofacial Microsomia Overview
{{Medical resources , DiseasesDB = , ICD10 = {{ICD10, Q, 90, , q, 90 , ICD9 = {{ICD9, 758.0 , OMIM = 164210 , OMIM_mult = , MedlinePlus = , GeneReviewsName = , ICDO = , eMedicineSubj = , eMedicineTopic = , MeshID = D006053 Congenital disorders Rare syndromes