Moebius syndrome: The rare condition that makes people unable to smile

A black and white photo of a child with an emotionless face.

Disease name: Moebius syndrome

Affected populations: The exact incidence of Moebius syndrome is unknown. A 2021 survey in Italy suggested that the condition affects 0.3 in 100,000 newborns in the country, while a 1996 Dutch study estimated that it affects about 2.1 per 100,000 newborns in The Netherlands. Other studies estimate that, worldwide, between 1 in 500,000 and 1 in 50,000 babies are born with the syndrome.