f508 and 5T - looking for CRMS experiences


New member
My daughter is a year and a half and has the mutations df508 and 5T (we aren't sure her TG length as they don't test for it where we live). She was positive on newborn screening but has had 2 negative sweat tests since (17 and then 28). She is being followed as someone with CRMS. I'm wondering if there are any updates from other CRMS parents about their experiences (I haven't been able to find any recent posts) as it is an extremely difficult "diagnosis" to wrap your head around. I know everyone's paths are different but I would love to connect with others who may understand/can relate. I'm afraid my daughter's sweat test is going to just keep climbing but our doctor assures us that sweat tests go up and down and she feels they are just one small piece of the puzzle (in her experience sweat test numbers don't always correlate with symptoms for the CRMS population). My daughter has had many ear infections which meant lots of antibiotics which led to C. Diff... it feels like she's been sickly but I think it's all unrelated.

Anyways I would just love to hear other's stories.

Thank you so much for your time.


New member
Sorry to hear the screening result. Your daughter has one copy of functioning CFTR, but the expression of this one copy is determined by another protein called TDP-43. Newborns have high TDP-43 expression, and normally would gradually lose it when they grow, which may explain the sweat test results. When TDP-43 is too high, it binds to the TG repeats that follows the 5T sequence and makes the CFTR shorter and non-functional. As long as TDP-43 is kept low, there should be enough CFTR expressed from the one copy of CFTR gene. But it is currently not well understood how the expression of TDP-43 might be induced. Your daughter likely has 12 TG repeats, which is more common. The symptom would be more severe if there are 13 TG repeats.


Active member
My mutations are Delta F08 and V562i with Variants 5T & 12T. I am 79 years of age. If she has not a COMPLETE CYSTIC FIBROSIS SEQUENCING, I would suggest that you request this of her CF Specialist.


New member
Hi! My son has a CRMS dx. He just turned 5. We are still pretty grey. He goes to clinic every 3 months and ENT every 6. He has some milder issues but so far nothing that makes them want to change his diagnosis. His sweats are still negative. We are just plugging along. If you aren't already in it there is also a FB group for CRMS families with a lot of 5t families. You should be able to find it if you search for CRMS but if not let me know and I can send you a DM with the link.