Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease characterized by an isolated, persistent thrombocytopenia in absence of known causes. In this review, we briefly analyze the most important diagnostic criteria of this autoimmune disorder, with particular consideration to differential diagnosis (false thrombocytopenia, congenital thrombocytopenia, acquired thrombocytopenia, pregnancy-associated thrombocytopenia) and to therapeutic options.