Abstract
Patients with a Philadelphia chromosome-negative myeloproliferative neoplasm may develop a lymphoproliferative disorder; however, the clinical and molecular determinants and the chronological onset of the two events remain unknown. We herein report the case of a 64-year-old man with concomitant diagnosis of high-risk essential thrombocythemia with evidence of a thrombotic event and high-count monoclonal B-cell lymphocytosis (high-count MBL). The patient harbored a JAK2V617F mutation and one of the most common genetic alterations found in chronic lymphocytic leukemia (CLL) (del 13q), which may represent a sign of disease progression. He was initiated on cytoreductive therapy with hydroxyurea 500 mg 3 times per week and hypocoagulation treatment, and is currently under regular surveillance of MBL without CLL criteria.