Immune Thrombocytopenic Purpura: Late-Onset Thrombocytopenia Following Mild COVID-19 Infection.

Immune thrombocytopenic purpura (ITP) is an acquired autoimmune disorder characterized by immune-mediated platelet destruction and impaired platelet production. Secondary ITP may occur following infections, including coronavirus disease 2019 (COVID-19); while thrombocytopenia is frequently observed in severe COVID-19, delayed-onset ITP after a mild, non-hospitalized infection is uncommon. We report a previously healthy 35-year-old man who presented with spontaneous epistaxis, widespread petechiae, and oral hemorrhagic bullae 14 days after a mild, home-managed COVID-19 infection. Laboratory evaluation revealed isolated severe thrombocytopenia (platelet count 2 x 10³/μL) with normal hemoglobin, leukocyte count, coagulation parameters, and peripheral blood smear; autoimmune and infectious workup was negative, and a prior platelet count had been normal. COVID-19-associated secondary ITP was diagnosed. Given high-risk bleeding manifestations, oral prednisone (1 mg/kg/day) and a single dose of intravenous immunoglobulin (1 g/kg) were initiated, with platelet counts increasing to 43 x 10³/μL by day 5 and normalizing within one week, remaining stable at day 75. This case highlights that severe ITP may develop during the recovery phase of even mild COVID-19, underscoring the importance of clinical vigilance and prompt immunosuppressive therapy.