In elementary school, the other children had whispered about Rick's behaviour. He had placed his books under his chair in the same spot every day. His pencil always had a sharp point and was positioned at the top of his desk, exactly in the middle. An eraser was kept on the upper right had corner, not too close to the edge.  His papers always were arranged carefully in the middle of his desk. This has continued in secondary school.

As a secondary school student, Rick has few friends. He doesn't like having visitors to his house because it takes too much effort to put things back in order after they leave. It bothers him when furniture and equipment are moved in his classrooms, or there is an unanticipated change in routine at school. He is easily upset when other students come close to his desk; some of the other students have noticed this and take pleasure in teasing Rick by threatening to mess up his papers. Consequently, he frequently watches the clock and begins to pack up his belongings several minutes before the end of the period.

Answer these three questions about the above case study:

1. What diagnosis, if any, best explains Rick's behaviour?

2. What observations support your diagnosis?

3. What more do you need to know to make the diagnosis with greater certainty or to explore other possible diagnoses?  How would you get this information?