Interestingly, many patients with ET may develop a rebound in platelet count during the postpartum course, which increases the risk of thrombosis during this prothrombotic period.[11] Herein, we present a case of type 2 calreticulin-mutant ET, who stopped her regular Pegylated Interferon Alfa-2a dose during pregnancy on her own and developed a marked rebound in her platelet counts during the postpartum period. Here, CALR is linked to essential thrombocythemia.