Personality disorders are grouped into three clusters, A, B, and C. One crude, but potentially helpful way to think about them is as the odd, the dramatic, and the anxious. We'll take each cluster alone in a post. Let's start with "the odd"--cluster A. Our quick-study summaries of each cluster A diagnosis follows:
PARANOID PERSONALITY DISORDER. Pervasive distrust and suspiciousness of others such that their motives are interpreted as malevolent.
SCHIZOID PERSONALITY DISORDER. Pervasive pattern of detachment from social relationships and a restricted range of expression of emotions in interpersonal settings.
SCHIZOTYPAL PERSONALITY DISORDER. Pervasive pattern of social and interpersonal deficits marked by acute discomfort with close relationships and cognitve or perceptual distortions and eccentricities.
Paranoid PD is clear enough. Schizoid and schizotypal might be confused without a little bit of extra attention. Note that people with schizoid personality disorder don't desire close relationships and choose solitude. People with schizotypal personality disorder aren't uninterested in relationships, they're socially anxious. Schizotypal PD includes among its criteria odd beliefs, magical thinking, bodily illusions, and paranoid ideation. Intense eccentricity.
All three of these share a criteria: Does not occur exclusively during the course of schizophrenia or other disorder with psychotic features.
Hope this helps. Thanks for all you do!