'Everyone is a cousin': What is Spoan syndrome, the genetic disorder plaguing a Brazilian village?

For years, families in a small Brazilian town, Serrinha dos Pintos, watched their children slowly lose the ability to walk, and no one knew why. Thanks to biologist Silvana Santos and her research of 20 years, the village now has an answer: Spoan syndrome. The disorder manifests when a person inherits the same mutated gene from both parents

Explainers