Immune thrombocytopenic purpura (ITP) is characterized by decreased platelet numbers secondary to platelet destruction and reduced platelet production. Even if the ITP persists, it typically responds to 'ITP-specific' therapies, such as intravenous immunoglobulin, steroids, intravenous anti-D, and splenectomy. Several reports, including our previous study, have implicated cytomegalovirus (CMV) in the pathogenesis of infrequent cases of ITP that were not severe in nature. A recent study from China suggested that CMV is the aetiology of some cases of acute ITP of childhood and may require different treatment. We report two adult and two paediatric patients with refractory, severe, symptomatic thrombocytopenia, who were diagnosed with ITP and found to have active CMV infection. Their presentations included fever, transaminitis, neutropenia, and atypical lymphocytosis, but in particular, treatment-refractory, severe ITP. Treatment with steroids appeared to worsen the CMV-ITP. All four cases showed improvement in platelet counts within two weeks of starting ganciclovir and cytogam and tapering steroids. Based on the four patients described here, we believe that, in certain cases, CMV infection will result in symptomatic, severe, refractory ITP, which may be indistinguishable from typical ITP. Eradication of CMV with antiviral therapy improved the ITP in these cases.