Peripheral arterial disease (PAD), maybe? You could google that term to see if the other symptoms resonate for him. How old is he? I think it would be a good idea for him to see his doctor, regardless, especially since he's getting more of these marks.
Hi. it could be Livedo Reticularis. have a look at this page http://www3.dermis.net/dermisroot/en/42784/diagnose.htm
and see if this is any use. I am covered in it from head to toe, and my dermatologist cant do anything about it.