Primary immune thrombocytopenia (ITP) is an acquired autoimmune bleeding disorder, accounting for about 1/3 of clinical hemorrhagic diseases. Loss of immune tolerance leading to increased platelet destruction and decreased platelet production is the main pathogenesis of ITP. Dysbiosis of the gut microbiota was found in many autoimmune diseases like rheumatic arthritis(RA),inflammatory bowel disease(IBD),multiple sclerosis and probiotic treatment or fecal microbiota transplantation(FMT) which can regulate the gut microbiota has good clinical efficacy in those disorders. One ITP patient with ulcerative colitis(UC) was treated with FMT and got progressive but significant increase in platelet level and lasted for several years.

The investigators are undertaking a multicenter, single-arm study of 60 primary ITP adult patients from 5 medical centers in China. All the participants are randomly divided into two groups to orally intake either probiotic supplements (n = 30) or placebo (n = 30) for 4 weeks in addition with high dose dexamethasone(40 mg/d for 4 days). Platelet count, bleeding and other symptoms were evaluated before and after treatment. Adverse events are also recorded throughout the study.

Inclusion Criteria:

• need of treatment(s) (including, but not limited to, low dose of corticosteroids) to minimize the risk of clinically significant bleeding. Need of on-demand or adjunctive therapy alone does not qualify the patient as refractory
• primary ITP confirmed by excluding other supervened causes of thrombocytopenia

Exclusion Criteria:

• pregnancy
• hypertension
• cardiovascular disease
• diabetes
• liver and kidney function impairment
• HCV, HIV, HBsAg seropositive status
• patients with systemic lupus erythematosus and/or antiphospholipid syndrome
• patients with known gastro-intestinal bleeding.
• use of antibiotics, prebiotics or probiotics in the past 4 weeks;