Otocephaly, also known as agnathia–otocephaly complex, 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).

[4] Otocephaly is generally a result of a de novo mutation in the gene PRRX1 on the long arm of chromosome 1.

Other extracranial malformations include neural tube defects, cephalocele, corpus callosum dysgenesis, renal ectopia, adrenal hypoplasia and rib, vertebral, or cardiac abnormalities.

The most severe cases, often called cyclopia-holoprosencephaly complex, are almost invariably lethal, and patients show intrauterine growth restriction, prematurity, and impaired ventilation.

Endotracheal intubation is difficult due to severe airway malformations, and only approximately 7 non-holoprosencephaly patients have survived beyond infancy.

In 2018, Indian neonatologist Kanwar Singh and his associates described a particularly severe case of otocephaly with cyclopia, agnathia, complete astomia and synotia.