Beyond the Usual Suspects: Rare Causes of Hemoptysis.

Hemoptysis is a potentially life-threatening phenomenon with a wide range of underlying causes. While most episodes are linked to common conditions such as infections, malignancy, or pulmonary embolism, a proportion of cases are due to unusual and often unexpected etiologies. This narrative review summarizes published case reports, series, and observational studies describing rare causes of hemoptysis, including vascular malformations, congenital anomalies, benign tumors, systemic diseases, and unusual infections. These conditions are frequently overlooked, which may delay recognition and appropriate management. The reviewed examples highlight the variety of diagnostic challenges and the broad spectrum of therapeutic strategies that may be required, ranging from endovascular procedures and surgery to targeted medical therapy. Despite advances in diagnostic methods, a subset of patients remain classified as having idiopathic or cryptogenic hemoptysis. For this reason, clinicians should keep a broad differential diagnosis in mind and remain aware of rare but clinically important entities. Awareness of these uncommon presentations and individualized patient management are essential for improving outcomes and avoiding missed critical diagnoses.