D27-08 Detection of Primary Ciliary Dyskinesia Through Prenatal Ultrasound Identification of Situs Inversus: A Case Series

Introduction Primary ciliary dyskinesia (PCD) is a rare, genetic disorder caused by dysfunctional motile cilia, resulting in impaired mucociliary clearance and chronic respiratory disease. Approximately 50% of individuals with PCD present with situs inversus totalis (SI), which can be detected by prenatal ultrasonography. Despite this potential early marker, the diagnosis of PCD is often delayed until late childhood. Untreated or inadequately managed, PCD is associated with progressive decline in lung function due to chronic infection and inflammation, whereas timely antibiotic prophylaxis and physiotherapy can preserve pulmonary function. Prenatal identification of SI represents an opportunity for early recognition of PCD, improved neonatal management and treatment. This study explores the clinical pathways following prenatal detection of SI, evaluates diagnostic approaches and timing, and explores how early recognition may influence clinical outcomes. Methods We conducted a retrospective case series of 18 children diagnosed with PCD and documented prenatal SI. Nine patients were included from Rigshospitalet, Copenhagen University Hospital (Denmark) and nine from University Hospital Münster (Germany). Data were obtained from clinical records using a structured search and entered into the EuropeanReferenceNetwork LUNG PCD registry. Results Prenatal detection of SI occurred between gestational week 20 + 4 and 41 + 2 (median: 33 + 7). Despite prenatal awareness of the laterality defect, PCD was not suspected before or immediately after birth in all cases. Management following the prenatal detection of SI varied widely, including amniocentesis, maternal genetic testing, delivery planning, neonatal care protocols, and specialist referrals (cardiologist, paediatric pulmonologist, clinical genetics). Neonatal respiratory distress occurred in 11/18 cases (64.7%), with 10 requiring NICU admission. The median age at first contact with a specialised centre was 2 months (range: birth - 7 years 8 months), and the median age at confirmed diagnosis was 4 months. Azithromycin prophylaxis was introduced during early childhood in most cases, though timing varied. All children received airway clearance therapy. The early clinical course varied, with a median of one respiratory exacerbation per year, a small proportion had chest-CT verified bronchiectasis before 10 years of age and spirometry indicated mildly reduced lung function in early childhood. Conclusion SI was detected prenatally in all cases, but subsequent management varied. The absence of a standardised approach to prenatal SI identification may lead to delayed or missed PCD diagnosis and treatment. Systematic guidelines are needed to optimise use of prenatal SI detection and improve long-term outcomes.