Subtypes
Millon
Psychologist Theodore Millon notes that because most patients present a mixed picture of symptoms, their personality disorder tends to be a blend of a major personality disorder type with one or more secondary personality disorder types. He identified four adult subtypes of avoidant personality disorder. Others
In 1993, Lynn E. Alden and Martha J. Capreol proposed two other subtypes of avoidant personality disorder:

Diagnosis
ICD
The World Health Organizations ICD-10 lists avoidant personality disorder as anxious (avoidant) personality disorder (F60.6). It is characterized by the presence of at least four of the following:
persistent and pervasive feelings of tension and apprehension;
belief that one is socially inept, personally unappealing, or inferior to others;
excessive preoccupation with being criticized or rejected in social situations;
unwillingness to become involved with people unless certain of being liked;
restrictions in lifestyle because of need to have physical security;
avoidance of social or occupational activities that involve significant interpersonal contact because of fear of criticism, disapproval, or rejection.Associated features may include hypersensitivity to rejection and criticism. It is a requirement of ICD-10 that all personality disorder diagnoses also satisfy a set of general personality disorder criteria. DSM
The Diagnostic and Statistical Manual of Mental Disorders (DSM) of the American Psychiatric Association also has an avoidant personality disorder diagnosis (301.82). It refers to a widespread pattern of inhibition around people, feeling inadequate and being very sensitive to negative evaluation. Symptoms begin by early adulthood and occur in a range of situations.
Loss and social rejection are so painful that these individuals will choose to be alone rather than risk trying to connect with others. Some with this disorder fantasize about idealized, accepting and affectionate relationships because of their desire to belong. They often feel themselves unworthy of the relationships they desire, and shame themselves from ever attempting to begin them. If they do manage to form relationships, it is also common for them to pre-emptively abandon them out of fear of the relationship failing.Individuals with the disorder tend to describe themselves as uneasy, anxious, lonely, unwanted and isolated from others. They often choose jobs of isolation in which they do not have to interact with others regularly. Avoidant individuals also avoid performing activities in public spaces for fear of embarrassing themselves in front of others. Symptoms include:

Extreme shyness or anxiety in social situations, though the person feels a strong desire for close relationships
Heightened attachment-related anxiety, which may include a fear of abandonment
Substance use disorders

Comorbidity
AvPD is reported to be especially prevalent in people with anxiety disorders, although estimates of comorbidity vary widely due to differences in (among others) diagnostic instruments. Research suggests that approximately 10–50% of people who have panic disorder with agoraphobia have avoidant personality disorder, as well as about 20–40% of people who have social anxiety disorder.