A 3-year-old boy presents with coarse facies, corneal clouding, hepatosplenomegaly, umbilical hernia, and dysostosis multiplex on X-ray. Urine mucopolysaccharide screen is positive with elevation of heparan sulfate and dermatan sulfate. Which enzyme is deficient in this condition?
- A Iduronate sulfatase (Hunter syndrome, MPS II)
- B N-acetylgalactosamine-4-sulfatase (Maroteaux-Lamy, MPS VI)
- C Alpha-L-iduronidase (Hurler syndrome, MPS I) ✓
- D Beta-glucuronidase (Sly syndrome, MPS VII)
Explanation
Hurler syndrome (MPS IH, MPS type I severe) is caused by deficiency of alpha-L-iduronidase, resulting in accumulation of dermatan sulfate and heparan sulfate. It presents in the first 1–2 years with coarse facial features, corneal clouding, hepatosplenomegaly, cardiac valve thickening, hearing loss, cognitive deterioration, and dysostosis multiplex. Hunter syndrome (MPS II) has the same glycosaminoglycan substrates but is X-linked, lacks corneal clouding, and is caused by iduronate sulfatase deficiency. Maroteaux-Lamy has dermatan sulfate only with preserved intelligence. Sly syndrome is very rare.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.