Hi, dear I have gone through your question. I can understand your concern. He has history of leukemia and diabetes. He now has dry gangrene. It is dry so no need to worry about spread of gangrene. It occurs due to lac of blood supply. No treatment is needed for that. Just continue anti diabetic drug and treatment of leukemia as per your doctor s advice. Hope I have answered your question, if you have any doubts then contact me at bit.ly/Drsanghvihardik, I will be happy to answer you. Thanks for using health care magic. Wish you a very good health.