問題解説・システム開発 : 内科医 米澤昌紘（れく）
A 60-year-old man presented with sensory disturbance of his fingers and toes. He lived alone and drank alcohol every day. The amount of his alcohol intake was over 60 g/day. He had muscle weakness and burning sensation of his extremities.
Examinations showed nystagmus and heart failure.
Which one of the following vitamins is related to his symptoms?
a. Vitamin A
b. Vitamin B₁
c. Vitamin B₆
d. Vitamin C
e. Vitamin D