(Hypoxanthine-Guanine Phosphoribosyltransferase Deficiency or HPRT Deficiency; Lesch-Nyhan Disease)
DefinitionLesch-Nyhan syndrome is a genetic disorder. It affects the metabolism of purines in the body. Purines are protein molecules that are important for the metabolism of RNA and DNA, which make up our genetic codes. Lesch-Nyhan syndrome is characterized by uric acid build-up, neurologic disability, and behavioral problems, including self-injury. It is a rare condition.
CausesLesch-Nyhan syndrome is caused by a mutation or change in a gene. This change results in the absence of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT). HPRT is needed to metabolize uric acid. Without this enzyme, uric acid builds up in the central nervous system, kidneys, and other areas of the body.This gene mutation occurs on the X chromosome. It can either be a new mutation in the affected person or inherited from the person's mother, who is a carrier.
Risk FactorsLesch-Nyhan syndrome is more common in men. Having male family members with Lesch-Nyhan syndrome (on your mother's side) also increases your risk.
SymptomsThe first symptom of Lesch-Nyhan syndrome may be orange-colored crystal-like deposits in the diaper. This may occur in children as young as 3 months. These deposits are caused by increased uric acid in the urine. Other symptoms include:
- Nervous system impairment:
- 4 to 6 months—lack of muscle tone and inability to lift the head
- 6 months—unusual arching of the back
- 9 months—inability to crawl or stand
- 12 months—inability to walk
- 12+ months—spasms of the limbs and facial muscles
- Blood in the urine
- Pain and swelling of joints
- Difficulty swallowing
- Behavioral problems and self injury occur in all cases
|Uric Acid Deposits in Joint|
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Self-InjurySelf-mutilating behavior is the hallmark of this disease. Children begin to bite their fingers, lips, and the insides of their mouths as early as 2 years old. As children grow, self-injury becomes increasingly compulsive and severe. Eventually, mechanical physical restraints will be necessary to prevent head and leg banging, nose gouging, loss of fingers and lips from biting, and loss of vision from eye rubbing, among others. In addition to self-injury, older children and teens will become physically and verbally aggressive.The cause of these behaviors is not entirely understood. However, some experts believe it is related to abnormalities in brain chemicals called neurotransmitters. It should be stressed that the child does not want to hurt himself or others, but is incapable of preventing these behaviors. People with Lesch-Nyhan syndrome have been described as doing the opposite of what they really want.
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