Sirolimus Monotherapy in the Treatment of Antiphospholipid Antibody Related Thrombocytopenia

The goal of this clinical trial is to learn the efficacy and safety of sirolimus in the treatment of anti-phospholipid antibody associated thrombocytopenia. The patients would be followed at 2 weeks, 1 month, 3 months, and 6 months after the enrollment. The main questions it aims to answer are the differences between sirolimus and control group at below outcomes: Primary outcome: the overall response rate at 6 months Secondary outcome: the complete response rate at 6 months the partial response rate at 6 months the change of anti-phospholipid antibody titers Participants will receive either sirolimus 1mg per day or placebo.