You are reviewing the complete blood count report of a patient who exhibits headaches and weakness. The report shows a red blood cell (RBC) count of 3.4 cells Ă— 106 (normal is 4.35 to 5.65 million red blood cells per microliter (mcL)), a white blood cell count of 7,500/microliter (normal is 4,500 to 11,000 WBCs per microliter , a platelet count of 200,000 (normal is 150,000 to 450,000 platelets per microliter) , hemoglobin levels of 10 g/dL (normal is 13.5 to 17.5 grams per deciliter), and hematocrit of 30% (normal is 38.3 to 48.6 percent). Which condition has the patient developed?