B105-06 Assessment of Alveolar Growth Disorder in People With Trisomy 21 Using Quantitative Computed Tomography (CT)

Abstract Rationale Trisomy 21, also known as Down syndrome, is a common chromosomal anomaly occurring in approximately 1 in 800 live births worldwide. There is pathological and CT evidence of alveolar growth disorder and development of subpleural cysts in people with trisomy 21, but the extent and incidence of subpleural cysts and alveolar simplification have not been widely reported 1. There is a growing body of evidence and interest in the use of quantitative CT imaging to better describe alveolar density, most often applied to adult lung disorders 2. We hypothesize that quantitative CT imaging can be used to assess the degree of alveolar growth disorder in pediatric patients with trisomy 21. Methods Our EMR was queried for all pediatric patients with trisomy 21 who had non-contrast CT chest performed between 2012 and 2025. We developed an adaptive quantitative threshold based on patient age, size and CT acquisition parameters by training a LASSO regression model on healthy pediatric controls to predict patient-specific lower limits of normal lung density, which ranged from -950 (school-age and adolescent patients) to -696 HU (infants). Three percent or greater lung volume below the low-density threshold was considered quantitively abnormal. Quantitative analysis of CT was performed to capture subpleural cysts and areas of low attenuation using recent Fleischner criteria, adapted for pediatrics 2. We then queried radiologist impressions from CT scans for the terms alveolar simplification, alveolar growth disorder, emphysema, subpleural cysts, or equivalent language. Results We identified 101 unique non-contrasted chest CT in patients with trisomy 21 (age 10 days to 17 years). Quantitative CT identified almost two times the number of cases of alveolar growth disorder than radiology impressions (49.5% v. 27.7%). This was primarily due to diffuse areas of low x-ray attenuation, interpreted as alveolar simplification, in the absence of a larger number of subpleural cysts, which were always identified on the radiology impression. Conversely, there were 17 patients identified on radiology impressions but not by quantitative CT; these were primarily characterized by subpleural cysts that represented 3% of total lung volume. Conclusion Quantitative CT is likely a complementary measure of alveolar growth disorder in this patient population, particularly in those with more intraparenchymal simplification and not just subpleural cysts. References 1. Biko, D et al. Pediatric radiology. 2008, 38(3), 280-84 2. San Jose Estepar, R et al. Am J Respir Crit Care Med. 2025, 211(5), 709-28 This abstract is funded by: None