A little town in South America is being ravaged by a mysterious problem as many local children have reportedly lost the ability to walk. Serrinha dos Pintos, in north west Brazil, is home to fewer than 5,000 people. However, it is where a new condition has been identified: Spoan syndrome. It is caused by a genetic mutation and affects the nervous system, weakening the body over the years. The syndrome only appears when the changed gene is passed down to an individual by both of their parents.

Silvana Santos has conducted research that has ended up revealing Spoan syndrome to the world, the BBC reports. Many of the patients she observed were cousins and married to each other, because of the settlement’s isolation and little inward migration. Much of the town’s population is related, so intermarriages are far more likely and accepted socially.

However, these relationships do come with a higher risk of mutations being passed down through the generations.

Santos was told that a female resident named Zirlândia experienced difficulties as a child, as her eyes moved involuntarily.

She then lost strength in her limbs and, in the end, needed a wheelchair.

A farmer, Lolô, whose daughter Rejane has Spoan, thinks the genetic change came from Maximiano, a “womaniser” in his family.

However, Santos found that the genetic mutation probably arrived more than 500 years ago with early European settlers in Brazil’s northeast – specifically related Sephardic Jews or Moors fleeing the Inquisition.

Inés, who is married to a second cousin, has two children: Chiquinho, 59, who can no longer speak, and Marquinhos, 46, who has limited communication abilities.

She said: “It’s hard to have a ‘special’ child. We love them the same, but we suffer for them.”

Larissa Queiroz, 25, who is Chiquinho and Marquinho’s niece, is also married to a distant relative.

But she and her husband, Saulo, discovered this only after several months of courting.

Larissa said: “In Serrinha dos Pintos, deep down, we’re all cousins. We’re related to everyone.”