JAK2V617F mutation is found in about 60% of cases of essential thrombocytemia (ET) and represents a driving mutation. Immune thrombocytopenia (ITP) is an autoimmune disease characterized by a low platelet (PLT) count. So far, only 2 reports described ET following ITP. For the first time we analyzed in a patient the JAK2V617F allele burden at ITP onset occurred 13 years before the ET diagnosis and found the presence of a small clone JAK2V617F positive clone (3%) raised to 27% in the following years. The association of ET and ITP could suggest similar pathogenetic mechanisms that should be further investigated.