A 4-year-old child has progressive gait disturbance, spasticity, and peripheral neuropathy. Nerve biopsy shows metachromatic brown granules on staining with cresyl violet. Urine sulfatide excretion is elevated. Which enzyme defect is expected?
- A Galactocerebrosidase
- B Arylsulfatase A (cerebroside sulfatase) ✓
- C Beta-hexosaminidase A
- D Sphingomyelinase
Correct answer: B. Arylsulfatase A (cerebroside sulfatase)
Explanation
Metachromatic leukodystrophy is caused by arylsulfatase A deficiency, leading to accumulation of cerebroside sulfate (sulfatide) in myelin-producing cells. Sulfatide granules stain brown rather than purple with cresyl violet, hence 'metachromatic', and the combination of central demyelination with a prominent peripheral neuropathy is characteristic. Galactocerebrosidase deficiency causes Krabbe disease, which shows globoid cells, not metachromatic granules.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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