attachment disorder is generally associated with children. your term, adult attachment disorder, seems to refer to persons who have a similar condition, but at a later age and stage of development. perhaps it is given to describe what a child with attachment disorder may become as an adult.
in children, attachment disorder is usually the result of an "absent" caregiver. that is to say, the primary contact person is either withholding, capricious, physically absent, or frequently changed. children growing up in such an environment develop insecure personas that have difficulty in the moment, and in later life, with sense of identity and interpersonal relationships. it is often said that attachment disorder is the first step toward sociopathy/BPD (depending largely upon gender).
generally, the treatment for attachment disorder in childhood is designed to generate more empathy and involvement in the primary caregiver, or to replace a dysfunctional caregiver. this to treat the cause, rather than the manifestation (a rare interdiction in modern psychology).
theory of mind is also involved in this question. some persons never learn that specific actions and facial expressions indicate certain desires or feelings. autistic persons suffer this disconnect. as such, they cannot see the expression of connection their caregivers make and rationalise it into an interpersonal connection.
an adult who grows up thru childhood with such a dysfunctional attachment will often manifest as entirely without compassion. they will see others around themselves as merely tools for self gratification. a sense of property rights will be lacking, and theft, vandalism, and wanton destruction of property will seem reasonable to them. impulse control and hoarding are also typical manifestations.
what do we do with such problematic personalities? re-parenting by a skilled terapist can be effective, if the client already realises that their current schema is problematic. this is a long term process and must be completed without change of providers. essentially, it is a re-training of the individual to teach them that they can trust another person to be consistent, thereby learning that the other person exists in a constant, thereby gaining respect for the other person, and thereafter, for themselves. in effect, it is an identity transfer process.