Lesch-Nyhan syndrome

Definition

Lesch-Nyhan syndrome is an inheritable disorder that affects how the body builds and breaks down purines. Purines are units in RNA and DNA, which make up the body's genetic blueprint.

Causes

Lesch-Nyhan syndrome is inherited as an X-linked trait. Therefore, the disease is seen mainly in males. It is characterized by increased blood and uric acid levels and by the absence of the enzyme hypoxanthine guanine phosphoribosyltransferase (HGP).

Males with Lesch-Nyhan have delayed motor development followed by bizarre, sinuous movements and increased deep tendon reflexes. A striking feature of Lesch-Nyhan syndrome is self-destructive behavior characterized by chewing off fingertips and lips, if not restrained.

The excess uric acid levels cause children to develop gout-like swelling in some of their joints. In some cases, renal dysfunction develops because of the excess uric acid levels.

Symptoms

• Family history of Lesch-Nyhan syndrome
• Male infant with delayed motor development
• Movement disorder
• Destructive chewing of fingers or lips (self-destructive behavior)

Exams and Tests

A physical examination may show:

• Hyperreflexia
• Spasticity
• Choreoathetoid movements
• Compulsive self-destructive behavior
• Increased serum uric acid
• Increase excretion of uric acid, urine
• Decreased HGP levels in cultured fibroblasts

• Serum chemistry, uric acid
• Urine chemistry, uric acid
• Skin biopsy tissue culture (fibroblasts)

Treatment

No specific treatment exists for Lesch-Nyhan syndrome. Allopurinol has been tried, and although it decreases the uric acid concentrations, it does not improve the neurological outcome.

Some symptoms may be relieved with the drugs carbidopa/levodopa, diazepam, phenobarbital, or haloperidol.

Recent advances in recombinant DNA techniques have allowed the gene responsible for the production of HGP to be cloned. Attempts will be made in the future to insert this gene into a patient's genetic material to determine if it will correct the metabolic defect.

Outlook (Prognosis)

The outcome is likely to be poor, even with attempts to treat the condition.

Possible Complications

Severe, progressive disability is likely.

When to Contact a Medical Professional

Call your health care provider if signs of this illness appear in your child or if there is a history of Lesch-Nyhan syndrome in your family.

Prevention

Genetic counseling for prospective parents with a family history of Lesch-Nyhan syndrome is recommended. The carrier state of the mother may be determined by culture of skin fibroblasts. Half the fibroblasts will have normal levels of the HGP enzyme and the remaining half will have deficient or absent HGP.