Question

Explain the biochemical defect that leads to Lesch-Nyhan syndrome and suggest how the defect might cause the behavioral symptoms characteristic of the disorder.

Answer 1

Ans.Lesch-Nyhan syndrome  is an inborn error of purine metabolism.It occur due to absence or deficiency of the activity of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). This deficiency occurs due to mutations in the HPRT1 gene located on the X chromosome. HGPRT is an important enzyme of purine metabolism and because of its deficiency level of uric acid increases in blood and urine.

Behavioral symptoms-

• Self-mutilation is seen in approximately 85 percent of patients.These behaviors generally begin between the ages of two and three years. However, they can also develop during the first year of life or later during childhood. Self-injurious behavior may include repeated biting of the lips, fingers, hands, and repetitive banging of the head against hard objects. Some children may scratch their face repeatedly.
• behavioral abnormalities include aggressiveness and spitting.
• Difficulty in swallowing so vomiting is common and most affected children are underweight.