Essential Thrombocythemia

—A Comparative Study with Polycythemia Vera—

Abstract

Essential thrombocythemia (ET) is a clonal myeloproliferative disorder (MPD), characterized by persistant elevation of platelet count in the absence of known causes. Since thrombocytosis may occur in other forms of MPD, differential diagnosis, especially for polycythemia vera (PV), is not always easy.
Eight patients with ET and nine patients with PV were studied from May 1975 to June 1984. Followings were observed: (1) Predominancy in females was observed in patients with ET, (2) Thrombohemorrhagic complications and splenomegaly were observed in a half of the patients with ET, (3) Hematologically, the significant differences were found in hemoglobin level (p<0.01) and platelet count (p<0.05) between ET and PV, (4) Spontaneous in vitroe rythroid colony formation (BFU-E and/or CFU-E) was observed in some patients with ET (2/6), while it was found in almost all the patients with PV (6/7), and (5) Only one patient of ET transformed into acute leukemia.
From our study, although we can draw a line between ET and PV in most cases, there are some perplexing cases between the two in which differential diagnosis is difficult. We assume that ET and PV might be different manifestations of the same disease process.