This deformity of the infant ear is characterized by an underdeveloped and malformed outer ear. Microtia, which means “little ear,” occurs in about 1 in 6,000 births and is more common in people of Asian, Hispanic, and Native American descent. Men are also affected twice as often as women. The ear deformity usually affects only one ear (unilateral microtia), but in rarer cases it can also occur on both sides (about 20% of microtia patients). In most cases of microtia, the earlobe is present, but other parts of the ear may be missing or malformed. While microtia is a description of the outer ear, it often occurs in conjunction with an absence of the ear canal (canal or aural atresia) or a narrowing of the ear canal (canal stenosis).
What causes microtia?
Microtia is rarely inherited genetically (no family history in 95% of cases). However, the exact cause is often unknown, and it often occurs in connection with certain syndromes (e.g. hemifacial microsomia, Goldenhar syndrome or Treacher Collins syndrome). Contributing factors are maternal diabetes, prenatal alcohol consumption, or even prenatal exposure to the acne medication Acccutane, thalidomide, or mycophenolate. But the maternal diet also plays a role: Too little folic acid or carbohydrates can trigger microtia. Likewise, decreased oxygen or blood supply to the fetus during the first trimester is associated with microtia.