In gout, the key enzyme deficiency in the Lesch-Nyhan syndrome that leads to hyperuricemia and gouty arthritis is:

• A Adenosine deaminase deficiency
• B Purine nucleoside phosphorylase deficiency
• C PRPP synthetase overactivity
• D Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency ✓

Explanation

Lesch-Nyhan syndrome is caused by complete deficiency of HGPRT (an X-linked recessive disorder) — the enzyme responsible for the salvage pathway that recycles hypoxanthine and guanine back to their nucleotides (IMP and GMP). Without HGPRT, hypoxanthine and guanine are catabolized to xanthine and uric acid, causing severe hyperuricemia, gout, renal calculi, and the characteristic neurological features (self-mutilation, choreoathetosis, spasticity). PRPP synthetase overactivity is another cause of gout but without the neurological syndrome. ADA and PNP deficiencies cause immunodeficiency, not gout.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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