Diffuse Alveolar Hemorrhage (DAH) is a life-threatening clinical syndrome characterized
by bleeding from the pulmonary microcirculation into alveolar spaces. It typicially
presents with acute respiratory failure, anemia, and diffuse radiological infiltrates.
Importantly hemoptysis may be absent in up to half of cases. Etiologies are diverse,
encompassing systemic vasculitides, connective tissue diseases, coagulopathies, drugs,
infections, hemodynamic disturbances, and idiopathic processes. Histopathologically,
DAH manifests as one of three overlapping patterns: pulmonary capillaritis, bland
alveolar hemorrhage, or diffuse alveolar damage, which help guide diagnostic and therapeutic
strategies. Capillaritis, commonly associated with immune-mediated vasculitis such
as ANCA-associated vasculitis and anti-glomerular basement membrane disease, typically
necessitating prompt and aggressive immunosuppression. In contrast, bland hemorrhage
often reflects coagulopathy or hemodynamic factors, while diffuse alveolar damage
is linked to toxins, infections, or ARDS.
Prompt recognition and systematic evaluation are critical to optimizing outcomes,
given DAH’s high in-hospital mortality exceeding 20%. Diagnosis relies on a combination
of imaging, bronchoalveolar lavage (demonstrating progressively bloodier returns and
hemosiderin-laden macrophages), and targeted laboratory evaluation for vasculitis,
infection, and coagulopathy. Management includes patient stabilization with supplementary
oxygen or indeed ventilatory support, careful avoidance of ventilator-induced lung
injury, and etiology-directed therapy. High-dose corticosteroids, cytotoxic agents,
and rituximab remain central in immune-mediated cases, while plasma exchange is indicated
in anti-GBM disease and severe refractory hemoptysis. Antimicrobial therapy, drug
withdrawal, hemostatic interventions, and, in select cases, extracorporeal support
may also be required.
This review outlines the histopathological spectrum, etiologic categories, diagnostic
algorithms, and evidence-based therapeutic approaches to DAH, emphasizing the importance
of early multidisciplinary management to improve survival and functional recovery.
