The presence of V1617F mutations in the JAK2 gene, CALR, or MPL mutations in association with thrombocytosis, normal hemoglobin, and serum lactate dehydrogenase levels, and the absence of leukoerythroblastosis or dacryocytes is highly suggestive of ET, but definitive diagnosis requires a biopsy of the bone marrow [9, 11, 12]. The gene discussed is CALR; the disease is thrombocytosis disease.