Otocephaly

Otocephaly is a very rare and lethal cephalic disorder characterized by the absence of the mandible (agnathia), with the ears fused together just below the chin (synotia). It occurs in every 1 in 70,000 embryos. Otocephaly is a very rare and lethal cephalic disorder characterized by the absence of the mandible (agnathia), with the ears fused together just below the chin (synotia). It occurs in every 1 in 70,000 embryos. During early embryogenesis, many different organ systems begin development. Any disruption in these processes results in complex malformation that usually results in death. The first branchial arch will normally develop around the 23rd to 26th day of gestation, also known as Carnegie stage 10. Usually, failure of this will result in isolated agnathia, but otocephaly may occur in exceptional circumstances. After agenesis of the first branchial arch, no cure is possible. Otocephaly is generally a result of a de novo mutation. Mutations in the gene PRRX1 on the long arm of chromosome 1 have been in some medical cases. Autosomal trisomies, while prevalent in similar conditions like cyclopia, are uncommon in otocephaly. In addition to agnathia and synotia, other symptoms that manifest in otocephaly include: Sewall Wright described twelve grades of otocephaly. Grades 1 to 5 were isolated agnathia with no neurological defects. Grades 6 to 9 were cyclopia with holoprosencephaly. Grades 10 to 12 were aprosopus with absence of the prosencephalon and mesencephalon. In aprosopus, the face is entirely absent from the cranium, and one human case of aprosopus has been reported in modern history. In almost all cases, fetuses with otocephaly are naturally or electively aborted before birth. If the infant is carried to term, death occurs within minutes due to airway obstruction. Otocephaly was first described in 1717 by Dutch scientist Theodor Kerckring. In 1933, evolutionary biologist Sewall Wright performed a study on otocephaly on guinea pigs and gave otocephaly its name.