30 year old tattoo infection

I cannot find any information on this. My brother has a tattoo on his leg that he has had for 30 years. Last summer he started to have what looked like pimples in the tattoo area. He self treated, it would scab, fall off with this happening over and over again. It started to get larger pimples which had hard centers. He went to his family doctor who thought he should go to a wound care center because of the length. By this time it looked infected, very sore, red, warm. The specialist at the wound care center was not sure what it was but has ruled out a spider bite and MRSA, they even did biopsies which came back negative. He was given an antiobiotic, just finished, and salt patches to place daily on the open sore, which is about 1 1/2 inches in diameter. At the specialist today he was told that they felt it very well could be a reaction/infection from the tattoo, which is kind of hard to believe, as it is 30 years old. They are treating with the daily salt patches, along with cleaning sore daily. They advised him that he may have to have the entire tattoo, about 12 inches long on his calf, removed, and skin grafts done. We have been trying to find out information about this, and have been unsuccessful, hoping someone here has heard anything about this.