Hematological Abnormalities Beyond Lymphocytosis During Infectious Mononucleosis: Epstein-Barr Virus-Induced Thrombocytopenia

BACKGROUND: Thrombocytopenia during Epstein-Barr virus mononucleosis is well-known; however, no recent series have investigated its frequency, associated factors, and evolution. The present study aimed to investigate platelet count characteristics in adult patients with infectious mononucleosis. METHODS: We reviewed the clinical records of 400 patients admitted to the hospital with infectious mononucleosis (52.0% male; median age, 19 years [range, 15–87 years]), focusing on blood platelet counts, thrombocytopenia prevalence and outcomes. RESULTS: Thrombocytopenia (platelet count ≤150 ×10(9)/L) was present in 119 (29.7%) patients. Thirty-two (8.0%) patients showed platelet counts lower than 100 ×10(9)/L. Thrombocytopenia was severe (platelets <50 ×10(9)/L) in 6 (1.5%) patients. Thrombocytopenia was associated with a lower frequency of typical mononucleosis symptoms such as sore throat and lymphadenopathy, lower frequency of positive heterophil antibodies, higher serum bilirubin concentration and prothrombin time, lower blood leukocyte and lymphocyte count, lower concentration of serum immunoglobulin G and immunoglobulin A concentrations, and larger spleen size. Thrombocytopenia normalized quickly during follow-up. Only 2 cases required specific therapy. Platelet counts significantly increased during follow-up, even in cases without baseline thrombocytopenia. There were no significant hemorrhagic complications. CONCLUSIONS: Transient thrombocytopenia is common during infectious mononucleosis in adult patients. Patients with thrombocytopenia have distinct clinical and biological features; it is typically mild during infectious mononucleosis. Cases of severe thrombocytopenia are rare and were not associated with hemorrhagic complications in this series.