Eating disorders
Perfectionism has been linked with Anorexia Nervosa in research for decades. A researcher in 1949 described the behavior of the average "anorexic girl" as being "rigid" and "hyperconscious", observing a tendency to "[n]eatness, meticulosity, and a mulish stubbornness not amenable to reason [which] make her a rank perfectionist". So common are such traits as perfectionism and rigidity among anorectics, that they have been referred to in clinical literature as "classical childhood features of patients with anorexia nervosa" or classical premorbid personality descriptors of anorexia nervosa".Regardless of the prevalence of the full-fledged OCPD among eating disordered samples, the presence of this personality disorder or its traits, such as perfectionism, has been found to be positively correlated with a range of complications in eating disorders and a negative outcome, as opposed to impulsive features—those linked with histrionic personality disorder, for example—which predict a better outcome from treatment. OCPD predicts more severe symptoms of Anorexia Nervosa, and worse remission rates, however, OCPD and perfectionistic traits predicted a higher acceptance of treatment, which was defined as undergoing 5 weeks of treatment.People with Anorexia Nervosa who exercise excessively display a higher prevalence of several OCPD traits when compared to their counterparts who did not exercise excessively. The traits included self-imposed perfectionism, and the childhood OCPD traits of being rule-bound and cautious. It may be that people with OCPD traits are more likely to use exercise alongside restricting food intake in order to mitigate fears of increased weight, reduce anxiety, or reduce obsessions related to weight gain.
Only when these traits become extreme, maladaptive, and cause clinically significant impairment in several aspects of ones life should a diagnosis of OCPD be considered. Personality change due to another medical condition. Obsessive–compulsive personality disorder must be differentiated from a personality change due to a medical condition, which affects the central nervous system, and may cause changes in behavior and traits. Substance use disorders. Substance use may cause the advent of obsessive-compulsive traits. It is necessary that this is distinguished from underlying and persistent behavior, which must occur when a person is not under influence of a substance. ICD-10
The World Health Organizations ICD-10 uses the term anankastic personality disorder (F60.5). At least four of the following must be present:

Feelings of doubt
Perfectionism
Excessive conscientiousness
Checking and preoccupation with details
Stubbornness
Caution
Rigidity
Insistent and unwelcome thoughts or impulses that do not attain the severity of an obsessive-compulsive disorder. Millons subtypes
In his book, Personality Disorders in Modern Life, Theodore Millon describes 5 types of obsessive–compulsive personality disorder, which he shortened to compulsive personality disorder. Comorbidity
Obsessive–compulsive disorder
OCPD is often confused with obsessive-compulsive disorder (OCD). Despite the similar names, they are two distinct disorders. Some OCPD individuals do have OCD, and the two can be found in the same family, sometimes along with eating disorders.The rate of comorbidity of OCPD in patients with OCD is estimated to be around 15–28%.