Primary ITP is an autoimmune disease involving autoantibody- mediated platelet destruction, suboptimal platelet production, and T-cell-mediated platelet lysis. These processes cause a decreased peripheral blood platelet count, resulting in an increased susceptibility to bleeding events. Despite a marked increase in epidemiological research over the past decade, unresolved questions remain with regard to disease pathogenesis, treatment effectiveness, and co-morbid burden among adults with primary ITP. Using data from national disease registries and the medical literature, this dissertation aims (1) to characterise associations of functional, candidate SNPs in cytokine or cytokine receptor genes with primary ITP among Caucasian adults, (2) to assess the utility of autologous In-labelled platelet sequestration studies prior to possible splenectomy, (3) to evaluate the effectiveness of eradication therapy in elevating platelet counts in H. pylori-infected patients, (4) to document health-related lifestyle concerns, and (5) to characterise associations of primary ITP among adults with both arterial and venous thromboembolic events.