Effects of serum vitamin D on platelet function and bleeding in primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is an autoimmune mediated thrombocytopenia with destruction and impaired production of platelets. Though life-threatening bleeding can occur in ITP, bleeding symptoms are often mild relative to platelet count. ITP is also associated with an increased thromboembolic risk. Variations in platelet function may contribute to the bleeding and thrombotic phenotype of ITP. Vitamin D (VD) deficiency (VDD) has been linked to enhanced platelet function in healthy individuals and patients receiving dual antiplatelet therapy. As VDD is associated with several autoimmune diseases including ITP, we aimed to investigate the influence of serum VD levels on platelet function in ITP. We assessed P-selectin and activated GPIIb/IIIa expression in naïve and stimulated platelets, soluble P-selectin levels, bleeding severity, and mean platelet volume in 79 primary ITP patients from the Vienna ITP Biobank but found no association with VD levels. Thus, low VD levels do not correlate with enhanced platelet function in ITP. Further, bleeding was not associated with VD, adjusting for platelet count. In summary, VD does not seem to be the primary driver of platelet function in ITP.