This X-linked condition is due to the defective purine metabolism. In infant the serum uric acid concentration is in the gouty adult range. It is characterized by compulsive self-destructive behaviour as seen in this case: chewing of lip and tongue leading to mutilation. These children may chew their fingers. Other neurological signs like extrapyramidal choreoathetoid movements, hyperreflexia, ankle clonus and spasticity of the legs develop.