A 39-year-old man presented with worsening slurred speech, difficulty walking, and falls for 2 years. Examination found severe ataxia and enlargement of Achilles tendons. Brain CT demonstrated modest hyperdensity in cerebellar hypodense lesions. T2-weighted imaging revealed hypointensity in deep cerebellar white matter, more evident on susceptibility-weighted imaging. Magnetic resonance spectroscopy suggested lipid storage and mitochondrial dysfunction. The diagnosis of cerebrotendinous xanthomatosis (CTX) was confirmed by gene screening of CYP27A1 (Figure).