MRCP-0653

A 44 year-old electrician is referred to you complaining of increasing problems with concentration. He also complains of irregular jerky movements of his extremities and fingers. He consumes approximately 25 units of alcohol per week. His father was diagnosed with dementia at the age of 40. Apart from generalized choreiform movements, his neurological and systemic examinations were normal. Which of the following is the most likely diagnosis?