An infant presents with refractory seizures, severe hypotonia, and lens subluxation in the first week of life. Urinary sulfite is markedly elevated and plasma urate is undetectable. The enzymatic defect involves failure of incorporation of which trace element into the required oxidases?
- A Selenium
- B Manganese
- C Molybdenum ✓
- D Cobalt
Correct answer: C. Molybdenum
Explanation
Molybdenum cofactor deficiency abolishes the activity of all three molybdenum-dependent enzymes: sulfite oxidase, xanthine oxidase, and aldehyde oxidase. Loss of sulfite oxidase allows toxic sulfite accumulation, producing neonatal encephalopathy with seizures and lens dislocation resembling homocystinuria, while loss of xanthine oxidase eliminates urate production, giving undetectable plasma uric acid. Selenium is incorporated into glutathione peroxidases and iodothyronine deiodinases, none of which explains this biochemical triad.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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