Abstract
INTRODUCTION: Bone health screening is established in cystic fibrosis (CF). Given the unknown status of bone quality in primary ciliary dyskinesia (PCD), these recommendations have not been adopted. We aimed to evaluate the bone phenotype in PCD compared to healthy controls and CF. METHODS: In this exploratory cross-sectional study, we assessed bone mineral density (BMD) at the whole body and lumbar spine using dual-energy X-ray absorptiometry (DXA), and tibial bone microarchitecture using high-resolution peripheral quantitative computed tomography (HR-pQCT) in 15 individuals with PCD and 45 with CF, aged 12-20 years. Measures were compared to healthy controls matched one-to-one by pubertal stage and sex. Disease-to-healthy differences were compared between PCD and CF, and associations with body mass index (BMI), lean mass, and lung function were analysed. RESULTS: DXA-measured areal BMD and HR-pQCT-derived total volumetric BMD showed no differences between PCD and controls. HR-pQCT revealed reduced cortical thickness, area, and BMD at the ultra-distal tibia in PCD compared to controls. While PCD and CF did not differ, the PCD bone phenotype more closely resembled pancreatic-insufficient than pancreatic-sufficient CF. Dimensional cortical deficits were largely explained by BMI or lean mass, especially in CF, but remained reduced in PCD after adjustment, indicating potentially intrinsic disease-related alterations. Lung function did not clearly correlate with bone outcomes in PCD. CONCLUSION: Skeletal health appears compromised in young people with PCD. Despite mostly normal densitometry, tibial bone microarchitecture was altered. This study positions bone health as a research priority in PCD and supports the need for larger confirmatory studies.