Infants with Lesch Nyhan syndrome appear normal at birth but motor delay and low-muscle tone become obvious within the first few months of life. Dystonia and choreoathetosis (involuntary jerky movement of the body) usually develop towards the end of the first year of life. Dystonia is a disorder of muscle tone producing typical contractile spasms or fixed postures, which interfere with movement and speech development.
Feeding difficulties and hiatus hernia (where part of the stomach pushes its way through a hole/tear in the diaphragm) are common.
Most affected individuals have moderate or severe learning difficulties (see entry Learning Disability), although some have low-average intellectual abilities.
A build up of uric acid in the blood and urine results in kidney damage and the production of kidney stones. Some infants have severe kidney problems and may go develop kidney failure.
Self-injurious behaviour is reported in the majority of cases. Biting of the lips, inside of the mouth and tongue or of the fingers is common. This behaviour fluctuates and may be associated with aggressive outbursts towards carers and anxiety and depression in boys.