The Lesch-Nyhan syndrome.

TLDR: The authors suggest that these children with the Lesch-Nyhan syndrome may have a very low threshold for the activation of a mechanism that controls repetitive, compulsive, pain-causing behavior.

Abstract: The authors report their observations of five children with the Lesch-Nyhan syndrome and review the literature to describe the general characteristics of the disorder, the development and types of self-mutilative behavior, and the types of outward-directed aggression. The authors suggest that these children may have a very low threshold for the activation of a mechanism that controls repetitive, compulsive, pain-causing behavior. This factor may also explain other forms of self-destructive behavior in children and may represent the psychobiological basis for the development of masochistic behavior.