Not so much immunity issues, it’s because of our identical body frames. We fit the “classic” description of middle aged, tall, thin female with kyphosis and scoliosis who are most prone to get MAC. She was ahead of me in dx and tx and got eye problems from ethambutol. So my doctor stopped my tx at 6 months since being identical twins, I would get it too. After 3 years I wasn’t doing well, so he started me on them again with the goal of one year. Probably tmi, but it’s nice having this site where we all understand what each us us are going through and can get support.