Moebius syndrome is a rare neurological condition that primarily affects the muscles that control facial expression and eye movement. The signs and symptoms of this condition are present from birth.

Weakness or paralysis of the facial muscles is one of the most common features of Moebius syndrome. Affected individuals lack facial expressions; they cannot smile, frown, or raise their eyebrows. The muscle weakness also causes problems with feeding that become apparent in early infancy.

Many people with Moebius syndrome are born with a small chin ( ) and a small mouth ( ) with a short or unusually shaped tongue. The roof of the mouth may have an abnormal opening ( ) or be . These abnormalities contribute to problems with speech, which occur in many children with Moebius syndrome. Dental abnormalities, including , are also common.

Moebius syndrome also affects muscles that control back-and-forth eye movement. Affected individuals must move their head from side to side to read or follow the movement of objects. People with this disorder have difficulty making eye contact, and their eyes may not look in the same direction (strabismus). Additionally, the eyelids may not close completely when blinking or sleeping, which can result in dry or irritated eyes.

Other features of Moebius syndrome can include bone abnormalities in the hands and feet, weak muscle tone (hypotonia), and hearing loss. Affected children often experience delayed development of motor skills (such as crawling and walking), although most eventually acquire these skills.

Some research studies have suggested that children with Moebius syndrome are more likely than unaffected children to have characteristics of autism spectrum disorders, which are a group of conditions characterized by impaired communication and social interaction. However, recent studies have questioned this association. Because people with Moebius syndrome have difficulty with eye contact and speech due to their physical differences, autism spectrum disorders can be difficult to diagnose in these individuals. Moebius syndrome may also be associated with a somewhat increased risk of intellectual disability; however, most affected individuals have normal intelligence.