JAK2 V617F-positive essential thrombocythemia with subsequent development of immune thrombocytopenia: A case report.

RATIONALE: Although essential thrombocythemia (ET) and immune thrombocytopenia (ITP) have different etiologies, 3 previous reports have described ET development in ITP patients, all of whom were positive for the JAK2 V617F mutation. Here, we report the first published case of ITP following ET in the absence of other platelet disorders.

PATIENT CONCERNS: A 70-year-old woman with a five-year history of ET with JAK2 V617F mutation treated with hydroxycarbamide for five months presented with petechiae on her limbs.

DIAGNOSIS: Her platelet count was 3 × 10/L, with the immature platelet fraction being 29%. White blood cell count and hemoglobin level were normal. Bone marrow examination showed increased number of megakaryocytes, but no morphologic dysplasia in any lineage. G-band analysis revealed no abnormalities. Platelet transfusion and cessation of hydroxycarbamide did not affect the platelet count. Thrombocytopenia was unlikely to have been induced by drugs, heparin, systemic lupus erythematosus, or human immunodeficiency virus. Hence, a diagnosis of ITP was made.

INTERVENTIONS: The patient received oral prednisolone combined with intravenous immunoglobulin.

OUTCOMES: Her platelet count rose to 310 × 10/L and remained stable, while her steroid dose was reduced. Further blood tests revealed the presence of antibodies against Helicobacter pylori, and appropriate treatment was administered. Resumption of hydroxycarbamide did not induce thrombocytopenia.

LESSONS: Although ET and ITP have different etiologies, chronic inflammation and immune deregulation underlie both and may play an important role in the progression from one to the other. Further research is warranted to understand the relationship between ET and ITP.