I have this mutation as well as DF508. Back when they first did genetic testing on me, this mutation was still unknown, so I just found out about it when the testing was done again in order to see if I would be eligible for Kalydeco.
In reading about it, I learned that it seems to be associated with slower progression of the disease because for some reason it produces some working proteins along with the majority of non-working ones.
I'm 40 years old and was diagnosed at 7 months due to a bout with pneumonia from which I did not recover well. Once diagnosed and treated with antibiotic for PA and digestive enzymes, though, I improved and had a healthy childhood. IV antibiotics and hospital stays didn't happen for me (except as a baby) until my early 30s. I have PA and MRSA, and FEV1 was 56% at last check, I think. My FEV1 stayed in the 80s until a sudden unexplained drop a couple of years ago.