A 4-year-old boy has coarse facial features, hearing loss, stiff joints, hepatosplenomegaly, and dysostosis multiplex, but the corneas are clear on slit-lamp examination. His maternal uncle died of a similar illness. Urinary glycosaminoglycans show excess dermatan sulfate and heparan sulfate. Which enzyme is deficient?

• A Iduronate sulfatase ✓
• B Alpha-L-iduronidase
• C N-acetylglucosamine-6-sulfatase
• D Arylsulfatase B

Explanation

Hunter syndrome (MPS II) is the only X-linked mucopolysaccharidosis, caused by iduronate sulfatase deficiency, with dermatan and heparan sulfate in urine. Unlike Hurler syndrome (alpha-L-iduronidase deficiency, MPS IH), corneal clouding is characteristically absent in Hunter syndrome, which helps discriminate between the two in boys with X-linked family history. Arylsulfatase A deficiency causes Maroteaux-Lamy (MPS VI) with normal intelligence.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.