BACKGROUND Thrombotic thrombocytopenic purpura (TTP) in children is a rare life-threatening syndrome, characterized by microangiopathic hemolytic anemia, thrombocytopenia with renal dysfunction, neurologic symptoms, and fever. TTP is usually caused by deficient activity of von Willebrand factor cleaving protease (ADAMTS13), due to either gene mutations or acquired via anti-ADAMTS13 autoantibodies. It can be triggered by bone marrow or solid organ transplantation, cardiothoracic-, abdominal-, and orthopedic surgeries, infections including very rarely Helicobacter pylori infection. CASE REPORT Here we report a case of a 16-year-old male with TTP, who presented with thrombocytopenia before an appendectomy. Seven days after surgery, our patient started to vomit, developed melena, and was admitted to our pediatric intensive care unit (PICU) with clinical presentation of shock. Gastroscopy revealed H. pylori positive hemorrhagic gastritis. The patient was treated by erythrocyte transfusions, fresh frozen plasma, human albumin, glucose-electrolyte solutions, vitamin K, platelet transfusion before implantation of central venous catheter, and antibiotics. After 36 hours, we started plasma exchange (PEX). Blood tests showed deficiency of ADAMTS13. Due to the presence of anti-ADAMTS13 autoantibodies, rituximab was administered. Due to generalized tonic-clonic seizures, he was artificially ventilated. Brain MR angiography showed small ischemic cerebro-vascular insult in the arteria cerebri media region. Despite immunosuppressive therapy and PEX, the patient did not improve completely until the H. pylori infection was eradicated. After which, he recovered completely. CONCLUSIONS We present a rare case of TTP accompanied with appendicitis and gastritis caused by H. pylori, where TTP improvement was dependent on H. pylori infection eradication.