TOPIC: Lung Pathology TYPE: Fellow Case Reports INTRODUCTION: Pulmonary arteriovenous malformation (PAVM) is rare cardiopulmonary vascular abnormality caused by the abnormal connection between pulmonary arteries and venous systems, more commonly associated to congenital disorders. More than 80% are congenital, and of these 47%–80% are associated with Osler-Weber-Render disease or hereditary hemorrhagic telangiectasia (HHT). Although most patients are asymptomatic, can cause dyspnea from right-to-left shunt, and the degrees of hypoxemia will be determined by the size of the shunt. PAVM was first described in 1897 by Churton, and even though the prevalence of PAVMs may be 1 in 2600 individuals, the condition is underdiagnosed and poorly understood. PAVMs may be single or multiple in occurrence and the incidence of single PAVMs ranges from 42% to 74%. CASE PRESENTATION: Case of a 48-year-old man with hypertension, GERD, testicular leydig cell tumor status post left orchiectomy and hypogonadism presented to his gastroenterologist with persistent abdominal pain refractory to medication. Upon review of systems, stated progressive dyspnea on exertion of one-year duration after orchiectomy, with associated fatigue. Denied any history of dizziness, syncope, epistaxis, hemoptysis, chest pain, palpitations, or cough. Physical examination was unremarkable and peripheral saturation at 99% at room air. Chest X-Ray with no cardiopulmonary pathology. Given persistent abdominal pain, abdominal CT scan was ordered, and a right lower lung lobe AVM was identified. CT angiography of the chest confirmed the presence of PAVM arising from the peripheral branches of the right pulmonary artery and feeding artery measuring 4mm. Radionuclide perfusion lung scan was compatible with a right to left shunt of 12%. Pulmonary function test done with the 100% oxygen and ABGs showed normal spirometry and estimated a shunt fraction of 15%. Bubble Study with evidence of PAVM. Considering patient is symptomatic he was scheduled for embolization. DISCUSSION: For many years, PAVM has been underdiagnosed and poorly understood, other symptoms include hemoptysis, chest pain, palpitations, epistaxis, and cough. Most patient are asymptomatic, confirmed patients should be screened for cerebral malformation by contrast enhanced head CT scan or magnetic resonance imaging given the high risk of stroke and brain abscess. Treatment must be offered to all symptomatic patients whereas asymptomatic patients should be evaluated on case to case basis. The treatment of choice for PAVMs is embolization, especially if the feeding vessel is larger or equal than 3mm. Follow-up with Thoracic CT Scan at 6–12 months must be performed to detect reperfusion of PAVM and opening of other occult PAVM. CONCLUSIONS: This case is intended to raise medical awareness on possible differential diagnosis of uncommon pulmonary causes of hypoxemia and dyspnea on exertion including pulmonary arteriovenous malformation. REFERENCE #1: Gossage JR, Kanj G. Pulmonary arteriovenous malformations. A state of the art review. Am J Respir Crit Care Med. 1998 Aug;158(2):643-61. REFERENCE #2: Shovlin CL. Pulmonary arteriovenous malformations. Am J Respir Crit Care Med. 2014 Dec 1;190(11):1217-28. REFERENCE #3: Shovlin CL, Condliffe R, Donaldson JW, Kiely DG, Wort SJ; British Thoracic Society. British Thoracic Society Clinical Statement on Pulmonary Arteriovenous Malformations. Thorax. 2017 Dec;72(12):1154-1163. DISCLOSURES: No relevant relationships by Onix Cantres-Fonseca, source=Web Response No relevant relationships by Vanessa Fonseca Ferrer, source=Web Response No relevant relationships by SULIMAR MORALES, source=Web Response