Spontaneous regression of essential thrombocythemia with MPL mutation on menopause.

Essential thrombocythemia (ET) is a subtype of myeloproliferative neoplasms. Approximately half of the patients with ET harbor a gain-of-function mutation in the JAK2 gene (JAK2-V617F), a small percentage have mutations in codon 515 of MPL (thrombopoietin receptor) gene, and the rest have neither mutation. Pregnancy is a rare complication of ET, and it has been reported that the number of blood platelets falls with pregnancy in ET patients and the number of blood platelets increases again after a delivery and this phenomenon is observed in JAK2-V617F-positive and JAK2-V617F-negative patients. We report the first case of an ET patient with MPL mutations, whose platelet count improved with the onset of menopause, not pregnancy, and the MPL mutation also simultaneously disappeared.