Idiopathic Thrombocytopenic Purpura Is More Severe in Children with a Recent History of Vaccination

Idiopathic thrombotic thrombocytopenia (ITP) the most common cause of acute onset thrombocytopenia in children, can be classified as primary (idiopathic) or secondary to different causal agents (drugs, vaccination, infections). This study is aimed to observe the severity of ITP based on the probable cause of the disease, specifically vaccination. This retrospective observational study surveyed the records of all patients, aged 1 to6 months, who were admitted with the diagnosis of ITP at Mofid children hospital in a 5 year period (2005-2010). Based on history of recent vaccination (< 6 weeks), patients were divided into two groups. The severity of ITP, described by the platelet count, was then compared between the recently vaccinated and not recently vaccinated groups. Severe ITP was defined as platelet count below 20,000/mm3. All ITP patients with concomitant diseases, diagnoses other than ITP, or simultaneous history of vaccination and probable virus infection were excluded. 51 patients were enrolled in this study (mean age = 3.86 ± 1.53 months; males = 32 [62.7%]). In 33 (64.7%) patients the platelets level was below 20000 /mm3. Thrombocytopenia following vaccination was observed in 25 (49%) patients. The number of patients with platelet count below 20000 /mm3 was significantly higher in the recently-vaccinated group (P value = 0.006). ITP was more frequent in the recently vaccinated children under 3 months of age (P Value = 0.03). In this study, a higher rate of more severe ITP in recently vaccinated young children was observed in comparison with other probable etiologies. Further investigations are needed to explain this finding.