65. A 59-year-old woman is admitted to the hospital because of a brief episode of right-sided hemiparesis. Medical history is significant for an eight-week history of bleeding from the gums, nosebleeds, throbbing and burning sensation in the hands and feet, and mild left upper quadrant pain. A blood panel shows a hemoglobin level of 15g/dL, hematocrit of 45% and platelet count of 900,000/mm3. Erythrocyte sedimentation rate, c-reactive protein, and WBC count are within normal range. Based on the patient’s symptoms and abnormal laboratory results, the patient begins treatment with hydroxyurea. Which of the following is the most likely diagnosis? *