My Grandson Is Being Tested For Hsp. I Understand This

My grandson is being tested for hsp. I understand this is an auto-immune disorder. My son and brother both have Crohn's Disease which is also an auto-immune disorder and another brother has a patch of hard skin on is thigh that he's been told is scleraderma, also an auto-immune disorder. All of these are familial so is it important for my grandson's physicians to be told of all this? What can be done for hsp? He has a rash on his face and legs that is under the skin.