Fields condition,[1] also known as Fields' disease,[2][3] is a neuromuscular disease that is considered the rarest medical condition in the world. It was named after Welsh identical twins Catherine and Kirstie Fields, who are two of only three people known to have been affected.[4][5][6]
One of them, called Field's Disease, is considered to be the rarest orphan disease, as only three people are known to have ever had it, two of them being the twin sisters Catherine and Kirstie Fields from Wales.