B105-11 The Clinical Course Of Pediatric Diffuse Alveolar Hemorrhage Syndrome, Through A Long-term Observation

Abstract Background Previous studies have reported that up to 50% of patients with diffuse alveolar hemorrhage (DAH) die within 2.5 years after onset. However, its clinical subtypes and disease course remain poorly defined. Some reviews have suggested that DAH often follows a ‘relapse-remission’ pattern, while a ‘progressive’ course is less common, though these claims lack detailed description or empirical evidence. This study retrospectively analyzed the long-term outcomes of children with DAH at our center to delineate patterns of clinical progression. Methods Retrospective analysis of 82 pediatric DAH patients (2010-2024) with 1 year follow-up at our institution. Results A total of 82 children were enrolled (male:female = 1:2.56). The median age at onset was 3 years (range: 0.3-12.4), and 67 (81.7%) were 6 years old. The median interval from onset to diagnosis was 3 months (range: 1 day-7 years).Follow-up ranged from 13 months to 13 years 8 months. Seventy-eight patients (95.1%) experienced relapse, with a median of 4 episodes (range: 1-17). Ten relapsed once, 61 relapsed 2-10 times, and 7 relapsed 10 times. Four patients remained relapse-free during follow-up (maximum 9 years 9 months). The median interval from initial treatment to first relapse was 8 months (range: 2-36); 59 patients (75.6%) relapsed within one year, including 13 (22%) in month 7.Based on clinical course, two major types were identified:1.Monocyclic type (25.6%, 21/82): remission after initial treatment with no or 2 relapses, showing a single-peak pattern with acute hemorrhagic and stable phases.2.Multicyclic type (74.4%, 61/82): 2 relapses after initial treatment, comprising acute hemorrhagic, absorption, chronic persistent, remission, or subsequent relapse phases. Subtypes included:Relapsing-remitting (39%, 32/82): recovery or minimal residual changes between relapses.Relapsing-progressive(31.7%, 26/82): progressive course or residual impairment after each relapse.Relapsing-secondary progressive (3.6%, 3/82): irreversible progression after later relapse, leading to severe respiratory dysfunction or death. Conclusions To our knowledge, this represents the first evidence-based characterization of clinical course patterns in pediatric diffuse alveolar hemorrhage (DAH). Two clinical courses patterns were identified: monocyclic and multicyclic. Approximately one-third of children exhibited a monocyclic course with favorable outcomes, while most demonstrated multicyclic courses, predominantly of the relapsing-remitting or relapsing-progressive types. Our findings indicate that the majority of patients were able to lead normal lives despite experiencing relapses over many years. Clinicians should recognize that recurrent relapses may represent an intrinsic feature of the disease rather than treatment failure. This abstract is funded by: None