Attachment disorder is something I've come across in previous jobs in relation to children I was working with. To put it simply - the kids I worked with hadn't formed an attachment to their mother (usually the case rather than the father as its the primary care giver which it stems from), as they hadn't been nurtured by her from a very young age. This lack of bonding/attachment shows itself in later years, along the lines of personality disorder, even psychopathic symptoms.
In the cases I worked with, the children had been in care from a very young age, as the mothers had been alcoholic and drug users (different children, different mothers). They had been passed around different carers, different family members and by the time they were teenagers, displayed concerning behaviours - one was quite violent, threatening to girls, very sly and devious. He would talk inappropriately about sex, had no concept of how other people felt. It was like he had shut off all his emotions. He didn't care who he hurt emotionally. It was put down to attachment disorder by his social worker. Its been a lot time since I worked in that area, so may not have explained it very well.
ETA Reading this back, sounds a lot like NM in some ways.