Sinusitis and Olfaction Improve in Young Children with Cystic Fibrosis Treated with ETI

OBJECTIVES: Evaluate if early therapeutic initiation may begin ameliorating olfactory dysfunction in addition to chronic rhinosinusitis in young children with cystic fibrosis. METHODS: Participants ≤ 10 years were enrolled across six U.S. cystic fibrosis centers (May 2023-December 2024). Data were collected at baseline and one year following therapeutic initiation. Mixed-effects models were adjusted for age, sex, and nasal steroid use. MEASUREMENTS: Sinus magnetic resonance imaging analysis included sinus volume, sinus opacification, olfactory bulb volume, olfactory cleft opacification, Lund-Mackay, and CRS-MRI scores. Psychophysical olfactory testing and quality of life assessments included the Pediatric Smell Wheel, Brief Questionnaire of Olfactory Disorders, EuroQol-5-Dimensions-Youth, and Sinonasal-5.Main Results: 31 participants (mean age 4.8 years) enrolled, 27 initiated treatment, and 26 completed follow-up (mean treatment duration 1.0 years). Following therapy, three olfactory measures improved: odor identification scores increased by 1.3 points (p = 0.03), olfactory bulb volume increased by 7.4mm3 (p = 0.02), and olfactory cleft opacification decreased by 14.4% (p = 0.004). Sinus opacification, Lund-Mackay, and CRS-MRI scores improved by 25.5% (p = 0.001), 5.0 points (p = 0.002) and 7.0 points (p = 0.005), respectively. Quality of life scores remained at near-normal levels. CONCLUSIONS: Children receiving therapy demonstrated improvements in olfactory function, olfactory structure, and sinonasal opacification. Predominantly stable, near-normal quality of life metrics preliminarily suggest symptom-based instruments alone may be insufficient to identify sinonasal disease and treatment response at this age.