Could be Graft Versus Host (GVH) syndrome...it happens after someone has had treatment for Leukaemia.
My son Ashley developed GVH after his TBI (Total Body Irradiation) and BMT (Bone Marrow Transplant). His skin fell off in sheets leaving him in terrible pain. High doses of morphine were the only thing that helped. Sadly Ashley didnt win his fight against Chronic Myeloid Leukaemia.
I am truly sorry to hear of your loss.