An 82-year-old male presented to the emergency department with an acute onset of chest pain and mild shortness of breath at rest. The pain in his left lower chest was pleuritic with intensity 9- on a 10-point scale. He had driven 2 h in his car that day, but had no other prolonged immobility. About 15 years previously, he was found to have increased hemoglobin (18.1 g/dL) and diagnosed with secondary erythrocytosis due to active smoking, chronic obstructive pulmonary disease (COPD), and residence in Payson, Arizona (altitude 4,999 ft). Polycythemia vera was entertained, but not pursued due to multiple secondary risks. He had been treated with daily aspirin and monthly phlebotomies to maintain a hematocrit below 45%. He also had a history of superficial thrombophlebitis, nephrolithiasis, hypertension and superficial transitional cell carcinoma of the bladder resected and in remission. There was also a deep venous thrombosis (DVT) and pulmonary embolism (PE) 13 years previously, believed to be provoked by prolonged immobility after a radical prostatectomy for prostate cancer now in remission. His medications were aspirin and lisinopril; he had no known drug allergies. He quit smoking 2 years prior after a 70 pack-year history. There was no other family history of thrombosis or bleeding disorder, autoimmune disorders, pulmonary disease or malignancy.