Abstract Background/Aims ANCA associated vasculitis (AAV) is a heterogeneous disease with significant mortality and morbidity. Diffuse Alveolar Hemorrhage (DAH) is a life-threatening condition and presents with hemoptysis, cough, breathlessness and respiratory failure. Studies have shown a prevalence of about 25%. This study was designed to assess the clinical features, serology, efficacy of treatment and long term outcomes in DAH patients secondary to AAV. Methods This was an observational study which included adult AAV Patients diagnosed based on Revised International Chapel Hill Consensus Conference classification criteria from January 2016 to August, 2023 after IEC approval. DAH was diagnosed based on clinical symptoms, Imaging (Diffuse alveolar infiltrates), drop in hemoglobin, hypoxia and Bronchoalveolar lavage in cases where feasible. Demographic details, clinical features, laboratory data including ANCA serology, treatment, disease activity, outcomes of patients were assessed prospectively. DAH and Non DAH groups were compared using Kruskal Wallis test for median values. Student t-test for mean values and Chi square for categorical variables were used to test association between two groups with statistical significance of P-Value <0.05. Results 133 AAV patients were included in the study. DAH was seen in 42(31.5%) patients. The mean (± SD) age of patients was 49.4(±18.9) years. Males (52.3%) were marginally higher in number then females (47.6%). Patients presented with a median of 8 weeks after AAV diagnosis. Hemoptysis (61.9%), cough (47.6%) and breathlessness(64.3%) were the presenting complaints. Renal, Sinusitis, Gastrointestinal involvement was seen in 83.3%, 61.9% and 14.2% respectively. Musculoskeletal and Ophthalmic features were seen in 33.3% each. RPRF was seen in 42.8%. c-ANCA, p-ANCA were seen in 73.8%,21.4% while Anti PR3 antibody and Anti MPO antibody were seen in 78.5%, 21.4% patients respectively. Median (IQR) BVAS score at presentation was 20(13-24) compared to 11(7-11) in Non DAH group which was statistically significant (p < 0.001). 10(23.8%) patients required ventilator support. IVIg was given in 3(7.1%), while plasmapheresis was used in 7(16.7%). Induction regimen with Cyclophosphamide was used in 73.8% and Rituximab (RTX) in 8(19%) patients. Maintenance RTX was used in 42.8% and 45.2% patients received Azathioprine. 23.8% patients relapsed and 54.6% patients were in remission. 10(23.8%) required Mechanical Ventilation. No patients were on long term oxygen therapy. 7(16.6%) patients died. Morbidity was seen in 16(38%) including CKD in 8(19%) patients. Median(IQR) duration of follow up was 10(6-24) months. Conclusion DAH is a serious manifestation of AAV and an important Rheumatological emergency. DAH was present in 31.5% with majority patients in remission. Mortality was seen in 16.6% and morbidity in 38% cases. Management with combination of Pulse steroids, Cyclophosphamide /Rituximab and Plasmapheresis is the key to better outcomes. Ventilator support may be necessary in severe cases. Timely diagnosis and aggressive management is the key to survival and prevents morbidity. Disclosure J.R. Yadavalli: None. K. Telang: None. P. Khatri: None. S. Dhuria: None. G. Ekbote: None. R. Gupta: None.