Sinus Disease in Young Children With Cystic Fibrosis

Inclusion Criteria: HEMT Group: * Children with documentation of a CF diagnosis * Age 2-8 years old at first study visit * CFTR mutation consistent with FDA labeled indication of highly effective modulator therapy (ivacaftor or elexacaftor/tezacaftor/ivacaftor) * Clinician intent to prescribe ivacaftor or ETI so that enrollment is before start of HEMT Non-HEMT/Control Group: * Children with documentation of a CF diagnosis * Age 2-8 years at first study visit * Ineligible for highly effective modulator therapy (ivacaftor or elexacaftor/tezacaftor/ivacaftor) based on CFTR mutation or clinical decision not to initiate HEMT if eligible Exclusion Criteria: For Both Groups: * Use of an investigational drug within 28 days prior to the first study visit * Use of ivacaftor or elexacaftor/tezacaftor/ivacaftor within the 180 days prior to and including the first study visit * Use of chronic oral corticosteroids within the 28 days prior to and including the first study visit. * Sinus surgery within 180 days prior to the first study visit