A 2-year-old boy presents with recurrent infections, coarse facial features, corneal clouding, hepatosplenomegaly, and developmental regression. Enzyme assay confirms alpha-L-iduronidase deficiency. This lysosomal storage disorder is classified as:

• A Hurler syndrome (MPS I-H) — autosomal recessive, severe phenotype ✓
• B Hunter syndrome (MPS II) — X-linked, without corneal clouding
• C Morquio syndrome (MPS IV) — with skeletal dysplasia but normal intelligence
• D Maroteaux-Lamy syndrome (MPS VI) — with normal intelligence

Explanation

Hurler syndrome (mucopolysaccharidosis type I-H) is caused by autosomal recessive deficiency of alpha-L-iduronidase, leading to lysosomal accumulation of dermatan sulfate and heparan sulfate. It presents in infancy with rapid cognitive decline, coarse facies, corneal clouding, organomegaly, dysostosis multiplex, and cardiac valvular disease. Death usually occurs in the first decade. Corneal clouding is a key distinguishing feature from Hunter syndrome (MPS II), which has the same enzyme pathway disruption but is X-linked recessive and lacks corneal clouding due to different enzyme involved (iduronate-2-sulfatase). Morquio syndrome and Maroteaux-Lamy syndrome have different enzyme deficiencies.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.