Don't ever think a person is in sin just because of their illness. Instead, pray. You don't know what the person is going through.
John 9:1-3 (KJV)
1 And as Jesus passed by, he saw a man which was blind from his birth.
2 And his disciples asked him, saying, Master, who did sin, this man, or his parents, that he was born blind?
3 Jesus answered, Neither hath this man sinned, nor his parents: but that the works of God should be made manifest in him.