TAFRO syndrome is a rare systemic inflammatory disease characterized by thrombocytopenia, anasarca, fever, reticulin fibrosis, and organomegaly. We encountered a case of calreticulin mutation-positive essential thrombocythemia (ET) with TAFRO syndrome-like features, followed by a rapid fatal course. The patient had been on anagrelide therapy for approximately three years for management of ET; however, she suddenly stopped going for follow-up and discontinued the medicine for a year. She presented with fever and hypotension, suggestive of septic shock, and was transferred to our hospital. The platelet count at the time of admission to another hospital was 50 × 104 / μL; however, it decreased to 25 × 104 / μL upon transfer to our hospital and further decreased to 5 × 104 / μL on the day of her death. In addition, the patient showed remarkable systemic edema and progression of organomegaly. Her condition suddenly worsened and led to her death on the 7th day of hospitalization. Postmortem, serum and pleural effusion interleukin (IL)-6 and vascular endothelial growth factor (VEGF) levels were significantly increased. Consequently, a diagnosis of TAFRO syndrome, since she met the diagnostic criteria for clinical findings and had high cytokine concentrations. Dysregulation of cytokine networks has also been reported in ET. Therefore, concurrent ET and TAFRO syndrome may have further triggered cytokine storms and contributed to the aggravation of the disease on development of TAFRO syndrome. To the best of our knowledge, this is the first report of complications seen in a patient with TAFRO syndrome due to ET.