A patient maintained on prolonged copper-free total parenteral nutrition develops a fusiform ascending aortic aneurysm and poor fracture callus formation. Which cuproenzyme defect accounts for the vascular lesion?

• A Lysyl oxidase deficiency preventing cross-linking of collagen and elastin ✓
• B Cytochrome c oxidase deficiency reducing oxidative phosphorylation in smooth muscle
• C Tyrosinase deficiency impairing melanin synthesis in vessel walls
• D Ceruloplasmin ferroxidase deficiency causing iron deposition in the tunica media

Explanation

Lysyl oxidase is a copper-dependent amine oxidase that oxidatively deaminates lysine residues in tropocollagen and tropoelastin, enabling aldehyde-derived cross-links that give connective tissue tensile strength. Copper deficiency weakens elastic laminae of great vessels, predisposing to aneurysm, and impairs bone matrix maturation. Cytochrome c oxidase deficiency explains the neurological features of Menkes disease, not aneurysm. Tyrosinase relates to pigmentation, and ceruloplasmin relates to iron mobilisation from stores.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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