Influenza A (H1N1) virus infection complicated by checkpoint inhibitor pneumonitis

RATIONALE: Checkpoint inhibitor pneumonitis (CIP) is a common, potentially severe adverse event in cancer patients receiving neoadjuvant immunotherapy, with glucocorticoids as the standard first-line treatment. Traditionally, glucocorticoids are avoided in confirmed viral pneumonia because they may delay viral clearance and increase secondary infection risk. No standardized strategy is available for managing concurrent CIP and viral pneumonia, and inappropriate treatment can lead to irreversible clinical deterioration. PATIENT CONCERNS: Following neoadjuvant immunotherapy, the patient developed concurrent influenza A (H1N1) infection and CIP, accompanied by persistent respiratory dysfunction and progressive pulmonary lesions. DIAGNOSES: Combined with the patient's immunotherapy history, respiratory symptoms, imaging changes, and positive influenza A (H1N1) etiological results, a final diagnosis of concurrent CIP and H1N1 viral pneumonia was established. INTERVENTIONS: The patient initially received antiviral and empirical antibiotic therapy. Due to ongoing clinical deterioration and poor response to anti-infective treatment, glucocorticoids were reinitiated to target CIP after comprehensive evaluation. OUTCOMES: The patient showed early radiographic worsening and intractable respiratory failure with no response to initial anti-infective management. After glucocorticoid administration, clinical symptoms and pulmonary lesions improved significantly, achieving a favorable recovery. LESSONS: Isolated antiviral and antibiotic treatment may fail to control disease progression in patients with concurrent CIP and influenza A pneumonia. Timely and rational glucocorticoid use can reverse clinical deterioration and improve prognosis even in the setting of active viral infection. This case provides practical evidence for the individualized management of overlapping CIP and viral pneumonia.