SNP Shot: Genomic Insights

Craniofacial microsomia is a condition encompassing a range of birth defects affecting the development of the skull and face. The term "microsomia" indicates abnormally small body structures. A key feature is facial asymmetry, where the right and left sides of the face differ in size and shape. While about two-thirds of individuals have abnormalities on both sides (though usually differing), others are affected on just one side. Common facial characteristics include underdeveloped upper or lower jaw (maxillary or mandibular hypoplasia), leading to dental issues, feeding difficulties, and speech problems. Severe mandibular hypoplasia can even affect breathing.

Ear abnormalities are common in craniofacial microsomia, often affecting one or both ears to varying degrees. These can include skin tags in front of the ear (preauricular tags), an underdeveloped or absent external ear (microtia or anotia), and a closed or absent ear canal, potentially causing hearing loss. Eye problems are less frequent, but some individuals may have an unusually small eyeball (microphthalmia) or other eye abnormalities leading to vision loss.

In some cases, individuals with craniofacial microsomia may also have abnormalities in other parts of the body. These can include malformed vertebrae, abnormally shaped kidneys, and heart defects.

Craniofacial microsomia has been referred to by various other names, often denoting specific combinations of signs and symptoms. These names are sometimes used interchangeably. Hemifacial microsomia is often used to describe craniofacial microsomia specifically with maxillary or mandibular hypoplasia. When hemifacial microsomia occurs alongside noncancerous eye growths called epibulbar dermoids, it may be referred to as Goldenhar syndrome or oculoauricular dysplasia.

Inheritance:

Most often, craniofacial microsomia occurs sporadically, affecting a single individual within a family and not being inherited. If the condition is related to a chromosomal abnormality, it may be inherited from a parent with the same abnormality, or it may occur as a new mutation in the chromosome in someone with no family history of the disorder. In a small percentage (1 to 2 percent) of cases, it is inherited in an autosomal dominant manner, requiring only one copy of a changed gene to cause the disorder. Rarely, it's inherited in an autosomal recessive manner, requiring two copies of a mutated gene. In this case, both parents carry one copy but usually don't exhibit symptoms. The specific gene or genes responsible for craniofacial microsomia are currently unknown.

In some families, there appears to be an inherited predisposition, rather than direct inheritance of the condition. In these instances, a combination of genetic and environmental factors might contribute to the development of craniofacial microsomia.