A 15-month-old girl who was normal until 12 months now has progressive spasticity, peripheral neuropathy with absent ankle jerks, and optic atrophy. Nerve biopsy shows Schwann cell lysosomes containing sulfatide granules that stain brownish-yellow with cresyl violet. Which enzyme is deficient?
- A Galactocerebrosidase
- B Arylsulfatase A ✓
- C Beta-hexosaminidase A
- D Sphingomyelinase
Correct answer: B. Arylsulfatase A
Explanation
Metachromatic leukodystrophy results from arylsulfatase A deficiency causing sulfatide accumulation in myelin. The stored granules stain brownish instead of blue-purple with cresyl violet, hence metachromatic, and this finding on nerve or marrow biopsy is diagnostic. Galactocerebrosidase deficiency causes Krabbe disease with globoid cells, hexosaminidase A deficiency is Tay-Sachs, and sphingomyelinase deficiency is Niemann-Pick disease.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.