Neurofibromatosis type I (NF-1) induced vasculopathy is rare but catastrophic complication after aneurysmal rupture. We present the case of a 55-year-old female who developed hypovolemic shock because of left internal mammary artery (IMA) pseudoaneurysm rupture associated with NF-1. Even she was not detected NF-1 at the time of arrival in emergency room. We decided to perform percutaneous embolization instead of surgical approach. In this case, after intervention, the ruptured left IMA aneurysm was well treated. After 10 days, the patient discharged without any complications. J Thorac Dis 2017;9(9):E739-E742 jtd.amegroups.com hematocrit (Hct), 32.2%. Three hours after the start of her examination, she reported dyspnea and chest pain that did not respond to analgesics; subsequently, she went into shock. Her blood pressure decreased to 60/40 mmHg; pulse, 98 beats/minute; respiratory rate, 20 breaths/minute; and oxygen saturation, 90% under a face mask with 10 L/min of oxygen. Hgb and Hct decreased to 5.6 g/dL and 16.7%, respectively. A computed tomography (CT) scan of the chest was performed, which showed active bleeding in the proximal left IMA and massive hemothorax accompanied by mediastinal shifting (Figure 1). Two units each of packed red blood cells and fresh frozen plasma were transfused; surgery and endovascular treatment were considered as treatment methods. We had previously surgically treated one patient with NF-1, 10 years ago, but the patient died. Since that case, we developed strategies for patients with NF-1, including performing interventional treatment, if possible.Taking into account the patient's unstable state and our surgical history with NF-1 patients, percutaneous embolization was chosen. The patient was transferred to the intervention room for the procedure. After approaching via the right common femoral artery, an angiogram was performed. Extravasation was observed at the site of a 1.1 cm × 1.0 cm pseudoaneurysm in the same location as the bleeding. We then performed a pre-ballooning procedure using interventional coiling. After superselective catheterization of the left IMA using a microcatheter and microwire, an embolization was performed using an Interlock coil (5 each). In a follow-up angiogram, no further extravasation was observed and no further treatment was required (Figure 2). The patient's clinical symptoms improved. She was transferred to the intensive care unit to be monitored for recurrent bleeding. A 24-Fr thoracic catheter was inserted and 1,300 mL of pleural fluid was drained, resulting in improvement of the dyspnea and hemothorax. The patient was transferred out of the intensive care unit 1 day after the treatment, and discharged 10 days after embolization, without any complications. Medication, consisting of acetaminophen 650 mg and tramadol Hcl 75 mg for pain control, was administered twice a day while she was hospitalized. There was no evidence of infection, therefore antibiotics were not used. Eighteen months later, the patient was healthy and had no finding...