[Cyclic thrombocytopenia diagnosed by periodic platelet count measurements].

Cyclic thrombocytopenia (CTP) is characterized by periodic platelet count fluctuations and is commonly misdiagnosed as immune thrombocytopenia (ITP) because of their similar clinical characteristics. Here, we present the case of a 74-year-old man with CTP diagnosed by weekly platelet count measurements. The patient initially developed mild bleeding symptoms with a platelet count of 0.8×104/µl. Bone marrow biopsy exhibited reduced megakaryocyte counts, an atypical characteristic of ITP. Weekly follow-up of platelet counts demonstrated an apparent cyclic pattern, resulting in CTP diagnosis. Regular platelet count measurements can help diagnose CTP in thrombocytopenia.