Fragile X syndrome (
FXS), also known as
Martin–Bell syndrome, or
Escalante's syndrome (more commonly used in
South American countries), is a
genetic syndrome. Nearly half of all children with fragile X syndrome meet the criteria for a diagnosis of
autism. It is an inherited cause of
intellectual disability especially among boys. It results in a spectrum of intellectual disabilities ranging from mild to severe as well as physical characteristics such as an elongated face, large or
protruding ears, and large testes (
macroorchidism), and behavioral characteristics such as
stereotypic movements (e.g. hand-flapping), and social anxiety.