Clinical Reasoning: A 47-year-old man with rapidly progressive ataxia and vitiligo

A 47-year-old man, with a medical history of vitiligo, presented to Peking Union Medical College Hospital for evaluation of progressive gait instability over a period of 10 months. He was initially noticed to walk with drunken gait and have difficulty performing accurate movements during goal-directed tasks. The patient also complained of difficulty in speaking and reported that objects appeared to move back and forth across his field of vision. The symptoms worsened, and he could not walk without assistance in the recent 2 months. There was no preceding infection or known family history of ataxia. The patient denied alcoholism.