@heathert My first pulmonologist never gave any reason for it when I asked. I guess she didn’t really know. Before I was diagnosed in 2016, (after the lung surgery to biopsy a large nodule), that specialist said nodules are caused by aspiration from acid reflux. Due to the inflammation acid reflux causes. The pulmonary Dr I have now said the nodules MAY be caused by the MAC MAI. I really believe none of them know exactly, or maybe it’s all of the above. I have a friend who said they saw nodules in her lungs on CT scan but she was never diagnosed with any NTM, although she does have acid reflux also. I guess the NTMs are because of the bronchiectasis, which she doesn’t have. I hope someday they figure it all out so we can know exactly how we should be treated.