1) A 28-year-old man returns for follow-up after treatment for deep-vein thrombosis. The deep-vein thrombosis was complicated by a non occlusive pulmonary embolus in the segmental branches of the left lower lobe and lingula, as seen on a CT angiogram of his thorax. He has no history of recent trauma or long-distance travel, and he does not smoke or use illicit drugs. The patient was treated with therapeutic low-molecular-weight heparin and transitioned to warfarin 5 mg daily by mouth. (Rivaroxaban was initially recommended, but there were cost concerns.) His international normalized ratio is 2.3, within the target range of 2.0 to 3.0. Laboratory results are shown below. What is the most likely diagnosis?
