So sorry for your loss Julie. Our oldest daughter passed away Feb 2013 at 2 years, 4 months old and carried both of these mutations. My second daughter carries DF508 and is fine. I just found out today that my newborn son's (9 days old) newborn screening has come back positive for CF with these mutations. We go in next week to run the sweat test to get the final diagnosis, but I guess we pretty much know already what the result will be.
There are almost 2000 known mutations. Someone with CF has 2 mutations. 2000 X 2000 = 4,000,000 possible combinations of mutations. 3% may sound like a rare combination but more common than the 3% would sound like.
All 3 of my cfers have this combo. All the same father and all different manifestations. I was also told G542X was the second most common mutation. Also told G542X usually involves the liver and in my case it has. I lost my first girl at 5 months. She was born with meconium ilius and lost most of her intestines. She had severe lung involvement and cirrhosis of the liver. The next cf child was a boy and he passed away when he was 15. Very severe cf. He had cepacia, cirrhosis and very compromised lungs. Also kidney failure and often septic. My next child with cf is a boy and he is now 17 and has only been hospitalized twice. He's got severe digestive issues including meconium ilius, DIOS, and CDiff. But a limited amount of lung disease although he does grow out cepacia every now again which he acquired from his brother but the cepacia hasn't given him a lot of trouble yet. He doesn't have cirrhosis but has fatty liver disease. All 3 from same mom and dad yet so different. So even if my children have the same gene mutations as other families the disease presents itself so differently it's not a perfect indicator!