These nerves control eye movements and facial expression. In newborns, the first symptom is an inability to suck. Deformities of the tongue, jaw, and limbs, such as club foot and missing or webbed fingers, may also occur.
Most patients have low muscle tone, especially in the upper body.
Mental retardation may also occur. As children get older, lack of facial expression and inability to smile become the dominant visible symptoms. Mobius syndrome may be accompanied by Pierre Robin syndrome, a disease in which there is an abnormally small jaw, downward displacement of the tongue, and a soft, cleft palate. It may also be accompanied by Poland's anomaly, a disease characterized by abnormal development of one side of the chest and limb deformities. There is no specific course of treatment for Mobius syndrome.