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An 11-year-old boy is brought to the office by his mother for a routine examination. She is worried that her son will be laughed at or bullied because of some unusual behaviors. The boy has a 4-year history of episodes in which he clears his throat, grimaces, and blinks his eyes. He has also recently started shrugging his left shoulder, which his mother fears is very noticeable to others. His medical history is otherwise unremarkable. The boy is having difficulty in math but is earning passing grades in other subjects. He has a few friends at school but prefers to play the piano and clarinet by himself after school. The mother notes that his shoulder movements stop when he plays a musical instrument. Physical examination is unremarkable with the exception of sporadic left-sided shoulder shrugs. Which of the following disorders is most likely to develop in this boy?