A 23-year-old woman has had altered consciousness and slurred speech for the past 24 hours. A head CT scan shows a right temporal hemorrhagic infarction. Cerebral angiography shows a distal right middle cerebral arterial occlusion. Within the past 3 years, she has had an episode of pulmonary embolism. A pregnancy 18 months ago ended in miscarriage. Laboratory studies show a false-positive serologic test for syphilis, normal prothrombin time (PT), elevated partial thromboplastin time (PTT), and normal platelet count. Which of the following is the most likely cause of these findings?

**Core Concept**
The patient's presentation with altered consciousness, slurred speech, and a head CT scan showing a right temporal hemorrhagic infarction, along with a history of pulmonary embolism and a false-positive serologic test for syphilis, suggests a hypercoagulable state. This state increases the risk of thrombosis in both arteries and veins.

**Why the Correct Answer is Right**
The patient's elevated partial thromboplastin time (PTT) and normal prothrombin time (PT) indicate a coagulation pathway defect. The patient's history of recurrent thrombosis, including a pulmonary embolism and a possible stroke, is consistent with a hereditary or acquired hypercoagulable state. The false-positive serologic test for syphilis may be related to the presence of a lupus anticoagulant, which is often seen in antiphospholipid syndrome (APS). The presence of antiphospholipid antibodies can lead to a hypercoagulable state, characterized by recurrent thrombosis and a prolonged PTT.

**Why Each Wrong Option is Incorrect**
**Option A:** Disseminated intravascular coagulation (DIC) is characterized by a prolonged PT and PTT, thrombocytopenia, and microangiopathic hemolytic anemia, which are not present in this case.

**Option B:** Factor V Leiden mutation is a common cause of hereditary hypercoagulability, but it would typically present with a normal PTT and a history of deep vein thrombosis.

**Option C:** Antithrombin deficiency is another cause of hereditary hypercoagulability, but it would typically present with a prolonged PTT and a history of recurrent venous thrombosis.

**Clinical Pearl / High-Yield Fact**
Antiphospholipid syndrome (APS) is a common cause of hypercoagulability in young women, particularly those with a history of recurrent miscarriage and thrombosis. The presence of antiphospholipid antibodies can be detected through a combination of clinical criteria and laboratory tests.

**Correct Answer:** D.

✓ Correct Answer: A. Antiphospholipid antibody