Diffuse alveolar hemorrhage with histopathologic manifestations of pulmonary capillaritis: Three case reports

BACKGROUND: Diffuse alveolar hemorrhage (DAH) is a multicause pulmonary capillary hemorrhage or pulmonary vascular small vessel injury (mainly capillaries, including arteries and veins), causing pulmonary microcirculation blood to accumulate in the alveolar space. DAH is classified by the histological absence or presence of pulmonary capillaritis (PC) and is rarely reported in the literature. CASE SUMMARY: This is a report of three girls aged 6-11 years with DAH and PC. Two patients had decreased hemoglobin and one had increased erythrocyte sedimentation rate. High-resolution computed tomography showed bilateral diffuse pulmonary infiltrate, and diagnosis of PC was confirmed by lung biopsy. Immunofluorescence test in one case showed granular IgG and a small amount of granular IgA deposit on the alveolar walls, and was negative in the other two cases, describing isolated pauci-immune PC. Treatment was with glucocorticoid alone or combination with immunosuppressants, and the symptoms resolved in all patients. CONCLUSION: PC is classified as isolated and immune-mediated PC associated with systemic disease. It can be controlled in most children with glucocorticoid alone or combined with immunosuppressants.