MSFinals-5636

MSFinals-5636

A 50-year-old man presented to the outpatient clinic with complaints of involuntary muscle movements of his tongue, fingers and trunk for the past 2 months. He was diagnosed with schizophrenia 20 years ago and has been on haloperidol, with good compliance. On examination, his temperature was 37.7 °C, blood pressure 115/80 mmHg and pulse 92 bpm. Respiratory rate was 14 cycles/min. There was pronounced choreoathetoid movement of his hands and fingers.
What is the most likely diagnosis of this patient?