An adult man who smears feces

A good friend of mine, a 55 year old man, holds down a job in computers - however, I doubt he will continue that work for long, as he refuses to bathe and of course has terrible body odor.
I had occassion to use his home bathroom unexpectedly recently and discovered the horror of what must be 'feces smearing'.  The walls, cupboards, sink, toilet, etc. were all smeared with feces - some had obviously been there for a very long time.
This man is kind, gentle, giving, clever, but has now begun to retreat from social contact with anyone.  His mother and I are greatly worried about him as he becomes more reclusive.  He has thwarted all of my attempts to stay in touch.  
Do these actions sound like they could be a part of an autism-related illness?  I am hoping to find a physiological or psychological 'diagnosis' in order to reassure his elderly mother that there may be a way to get him some help.  Even if we cannot convince him to get treatment, perhaps her mind would be eased to know that it isn't a character flaw or anything in his upbringing that has created his issues.
I do appreciate any feedback you may provide here.

[Rachel Thompson, Ph.D., BCBA]

It would be useful to identify a clinical social worker in your area who would be able to provide assessment and intervention services or recommend a more appropriate professional in your area. It will be important to get your friend some help soon. As you noted, the recent changes in his behavior may jeopoardize his job, which will further limit his opportunities for appropriate social interaction.