Haemoptysis Caused by Right Intercostal Artery-To-Pulmonary Artery Fistulas Mimicking Cryptogenic Haemoptysis.

Systemic artery-to-pulmonary artery fistulas (SA-PAFs) are rare vascular anomalies, typically associated with chronic pulmonary or pleural inflammation. SA-PAFs are categorised by their systemic arterial origin, arising either from the bronchial arteries or nonbronchial systemic arteries such as the intercostal arteries. Nonbronchial SA-PAFs are uncommon in patients without a history of thoracic trauma, surgery or infection. We report a 55-year-old man with recurrent haemoptysis caused by right intercostal artery-to-pulmonary artery fistulas, despite having no history of pulmonary or pleural disease. The diagnosis was established by selective angiography, and the lesions were successfully treated with coil embolisation. This case demonstrates that haemoptysis due to nonbronchial SA-PAFs can occur even in the absence of a history of the usual aetiologies and may be misclassified as cryptogenic haemoptysis. Even in patients initially diagnosed with cryptogenic haemoptysis, it is crucial to first perform a detailed vascular evaluation using CT angiography to identify hidden nonbronchial SA-PAFs.