Lesch-Nyhan syndrome: a rare genetic condition that results in neurologic and behavioral abnormalities. It occurs almost exclusively in males because it is inherited in an X-linked recessive manner. This means that the defective gene resides on the X chromosome. Rarely, females are affected because they have two X chromosomes, while males have one, and both copies of the defective gene (one on each X chromosome) would need to be present for a female to be affected. Lesch-Nyhan syndrome is associated with elevated levels of a chemical known as uric acid, which can cause gouty arthritis and kidney stones. The condition is caused by mutations in a gene known as HPRT1.
The neurologic and behavioral problems that occur in people with Lesch-Nyhan syndrome often include involuntary muscle movements, jerking movements (chorea), and flailing of the limbs (ballismus). Those affected typically cannot walk and are confined to a wheelchair. Self-injury, such as biting and head banging is a common behavioral problem in people with Lesch-Nyhan syndrome.