I think it’s very likely there’s a genetic component to both Bronchiectasis and MAC. My sister was diagnosed w/ Bronchiectasis some years ago. I wouldn’t be surprised if my Mother had it also. She was often clearing her throat, blowing her nose and coughing. And yes, it’s more common in post menopausal, slight women. There may also be an immune issue involved with the infection. However, when I talked to my specialist about it, he said, as of now, there’s no way to tell. There hasn’t been enough research done in this area. Maybe someday soon there will be.