Diffuse alveolar hemorrhage complicating influenza A infection in an immunocompetent infant: a case report and literature review

Background Influenza is a common cause of hospitalization in young children, particularly infants. While most infections are self-limited, severe and life-threatening complications may occur. Diffuse alveolar hemorrhage (DAH) is a rare pulmonary manifestation of influenza, predominantly reported in adults, and is exceedingly uncommon in immunocompetent infants. Case presentation We report the case of an 8-month-old previously healthy female infant who presented with influenza A infection and rapidly progressed to acute respiratory failure and shock despite antiviral therapy. Bleeding was noted from the nasal cavity prior to clinical deterioration, and during emergent endotracheal intubation, blood was observed flooding the bronchial tree, consistent with massive pulmonary hemorrhage. Flexible bronchoscopy showed diffusely erythematous and friable airway mucosa without an identifiable focal bleeding source, and early bronchoalveolar lavage was nondiagnostic. Nasopharyngeal testing confirmed influenza A (H3). Laboratory findings revealed severe systemic inflammation, leukopenia with neutropenia, and anemia with normal coagulation parameters. Chest imaging demonstrated bilateral pulmonary infiltrates. After exclusion of autoimmune, coagulation, immunodeficiency, and alternative infectious causes, a diagnosis of diffuse alveolar hemorrhage secondary to influenza A infection was established. The patient was successfully managed with supportive care, antiviral therapy, tranexamic acid, and empiric antibiotics, without corticosteroid treatment, and made a full recovery. Conclusions This case highlights that influenza A infection can cause diffuse alveolar hemorrhage even in immunocompetent infants. In this age group, DAH may present without overt hemoptysis, with pulmonary bleeding becoming apparent only after airway intervention. Prompt recognition, exclusion of alternative etiologies, and early supportive and antiviral management are crucial, while the role of corticosteroids in infection-associated DAH remains uncertain and should be individualized.