NEET PG / USMLE – MCQ 21

A 4-year-old boy has delayed motor development and choreoathetosis. He had normal development at birth. He chews his fingers and lips, which has resulted in tissue loss. He has arthritis. Serum and urine uric acid concentrations are increased. Which of the following abnormalities is the most likely cause of these findings?
(A) Adenine phosphoribosyltransferase deficiency
(B) Hypoxanthine-guanine phosphoribosyltransferase deficiency
(C) Increased cellular turnover of nucleic acids
(D) Increased conversion of hypoxanthine to inosine monophosphate
(E) Phosphoribosylpyrophosphate synthetase deficiency

Correct answer : (B) Hypoxanthine-guanine phosphoribosyltransferase deficiency

• This is a case of Lesch-Nyhan syndrome caused by deficiency of HGPRTase
• It is also known as Nyhan’s syndrome, Kelley-Seegmiller syndrome and Juvenile gout.
• Rare X linked recessive disorder
• Described by a medical student Michael Lesch and his mentor, pediatrician Bill Nyhan in 1964
• HGPRTase deficiency causes a build-up of uric acid in all body fluids
• This results in both hyperuricemia and hyperuricosuria and is responsible for the clinical features

Clinical features:

• Gouty arthritis
• Neurological features
• Poor muscle control
• Moderate mental retardation
• Self-mutilating behaviors, characterized by lip and finger biting
• Facial grimacing, Involuntary writhing, and repetitive movements of the arms and legs similar to those seen in Huntington’s disease
• Some develop megaloblastic anemia