目的 探讨以弥漫性肺泡出血综合征（DAHS）为首发表现的儿童抗中性粒细胞胞质抗体（ANCA）相关性血管炎（AAV）的临床特征、治疗及转归。方法 回顾性分析医院2010年1月至2023年12月收治的以DAHS为首发表现并最终确诊为AAV的6例患儿的临床资料。结果 6例患儿中女4例、男2例，DAHS起病中位年龄5.4（4~7.6）岁，AAV诊断中位年龄7.2（6.3~10.6）岁，DAHS起病至诊断AAV的时间间隔为6个月~3年。首次诊断DAHS时，6例患儿ANCA检测均为阴性。6例患儿均存在不同程度的贫血，均为抗髓过氧化物酶抗体、核周型ANCA阳性的显微镜下多血管炎。胸部影像学主要表现为肺弥漫性浸润，表现为片絮影、斑片影及磨玻璃影，痰液、胃液、支气管肺泡灌洗液或肺活检找到含铁血黄素巨噬细胞。6例患儿均存在不同程度的肾脏受累，所有患儿均予糖皮质激素联合免疫抑制剂或生物制剂治疗，2例患儿接受血浆置换，1例予腹膜透析治疗。随访24~84个月，6例患儿肺部病灶均较前明显吸收、减少，未再出现咯血、痰中带血，症状明显好转，其中1例进展为慢性肾脏病5期，予规律腹膜透析，病情稳定。结论 DAHS是AAV的一种严重并发症，首发表现为DAHS时可能缺乏AAV的其他特征性表现，造成诊断困难。临床医师应对此类情况提高警惕，尽早明确诊断，积极予激素联合免疫抑制剂或生物制剂治疗可有效改善预后。

Objective To investigate the clinical features, treatment and prognosis of pediatric ANCA-associated vasculitis (AAV) presenting initially with diffuse alveolar hemorrhage syndrome (DAHS). Methods A retrospective analysis was conducted on the clinical data of 6 children, admitted to the hospital from January 2010 to December 2023, who presented with DAHS as the initial manifestation and were eventually diagnosed with AAV. Results Among the 6 children, 4 were female and 2 were male. The median age at DAHS onset was 5.4 ( 4-7.6) years, while the median age at AAV diagnosis was 7.2 (6.3-10.6) years. The interval between DAHS onset and AAV diagnosis ranged from 6 months to 3 years. At the initial diagnosis of DAHS, ANCA testing was negative in all 6 children. All children exhibited varying degrees of anemia and were diagnosed as MPO/p-ANCA-positive microscopic polyangiitis (MPA). Chest imaging primarily showed diffuse pulmonary infiltrations, manifesting as patchy, flocculent, and ground-glass opacities. Hemosiderin-laden macrophages were found in sputum, gastric fluid, bronchoalveolar lavage fluid, or lung biopsy specimens. All 6 children had varying degrees of renal involvement. Treatment for all patients involved glucocorticoids combined with immunosuppressants or biologics. Two children underwent plasma exchange, and one received peritoneal dialysis. During a follow-up period of 24 to 84 months, pulmonary lesions in all 6 children showed significant absorption and reduction compared to previous imaging. No recurrence of hemoptysis or blood-streaked sputum was observed, and symptoms markedly improved. One patient progressed to chronic kidney disease stage 5, receiving regular peritoneal dialysis with stable condition. Conclusions DAHS is a severe complication of AAV. When presenting as the initial manifestation, DAHS may lack other characteristic features of AAV, leading to diagnostic challenges. Clinicians should maintain a high index of suspicion for such presentations. Early definitive diagnosis and aggressive treatment with glucocorticoids combined with immunosuppressants or biologics can effectively improve prognosis.