A 2-year-old child presents with progressive coarsening of facial features, corneal clouding, stiff joints, recurrent respiratory infections, and hepatosplenomegaly. X-ray shows 'J-shaped' sella and dysostosis multiplex. Urine shows increased dermatan sulfate and heparan sulfate. Which enzyme is DEFICIENT?
- A Iduronate-2-sulfatase (Hunter syndrome, MPS II)
- B alpha-L-Iduronidase (Hurler syndrome, MPS I) ✓
- C N-acetyl-glucosamine-6-sulfatase (Sanfilippo C, MPS IIIC)
- D Galactose-6-sulfate sulfatase (Morquio A, MPS IVA)
Explanation
The combination of corneal clouding, dysostosis multiplex, J-shaped sella, hepatosplenomegaly, and coarse facies with urinary dermatan sulfate and heparan sulfate is classic for Hurler syndrome (MPS I-H), caused by deficiency of alpha-L-iduronidase (IDUA gene). Hunter syndrome (MPS II, iduronate-2-sulfatase deficiency) is X-linked, lacks corneal clouding, and also excretes dermatan and heparan sulfate but corneal clouding is a distinguishing feature. Sanfilippo excretes only heparan sulfate. Morquio excretes keratan sulfate and presents with skeletal dysplasia without intellectual disability.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.