[Cyclic thrombocytopenia synchronizing with the menstrual cycle showing periodic phases of thrombocytopenia and rebound thrombocytosis].

A 37-year-old woman was admitted to our hospital for purpura involving the extremities and thrombocytopenia. Prednisolone (PSL) was administered based on a diagnosis of idiopathic thrombocytopenic purpura (ITP), but was not effective for maintaining her platelet count within the normal range, which showed cyclic fluctuation corresponding to the menstrual cycle. Therefore, we discontinued PSL, and cyclic thrombocytopenia (CTP) was diagnosed. CTP is a rare disease which is usually treated as ITP but with no response. Although the exact cause of CTP is uncertain, in our case, a hormonal mechanism may be responsible for fluctuating platelet count.