Polycythemia vera (NORD)

A 55-year-old woman with a history of peptic ulcer disease comes to her primary care physician because of generalized itchiness. She says these symptoms started a few months ago, and she noticed that it tends to get worse when she takes warm showers. She recently began experiencing sudden severe burning pains in her hands, after which they turn a reddish color, as shown below. Physical examination shows a well-developed female with diffuse ruddy cyanosis, elevated blood pressure, and splenomegaly. Laboratory studies show elevated erythrocyte count with increased mass, elevated platelet count, and decreased erythropoietin. Which of the following is the most likely diagnosis?