Histogram of the age at which symptoms of LNS became apparent (Brian, 2010).

Early signs of Lesch-Nyhan syndrome begin during a child's infancy. Excessive crying, irritability, and

(sometimes) an orange, grainy material within the diaper (from urine, not fecal matter) are the earliest signs of LNS, short of a karyotype via amniocentesis. During childhood, growth and development deficiencies, as well as physical and mental disabilities typically arise. Inhibited speaking abilities/motor skills are also soon apparent.

High concentrations of uric acid in the joints(known as hyperuricemia) are caused by LNS, which results in reduced muscle tone and slight muscular spasms. These muscle spasms are caused by choreoathetosis (involuntary muscular movement) induced by spasticity (mucular 'twitching' because of muscular stiffness), which is, in turn caused by the high concentration of uric acid in the system.

Obvious physical symptoms, such as self-mutilation in the form of finger(nail) biting to the point of personal injury, lip biting to the point of mutilation, and head banging against nearby objects, are caused by LNS. Commonly, affected individuals also exhibit unusual aggression and other unusual behavior (due to their mental handicapping). Gout is also frequently observed in people with Lesch-Nyhan syndrome.

The symptoms can be divided into three basic groups:

  • Physical and Mental Disabilites
  • Overproduction of Uric Acid
  • Behavioral Problems