A 51-year-old man had abdominal pain 12 hours before seeing a doctor. He was admitted to the previous hospital for the continuous abdominal pain. On the next day, he was referred to our hospital with abdominal pain and hypotension requiring use of an artificial respirator. He had no sore throat and no other symptom before the admission to the hospital. His past medical history was unremarkable, and he was not being treated with any drugs. A physical examination revealed hypotension, with a systolic blood pressure of 70 mmHg, for which noradrenaline 0.18 µg/kg/min was continuously infused. An abdominal examination revealed muscle guarding, rebound tenderness, and an erythematous macular rash over the trunk. A complete blood count revealed no anemia, a white blood cell count of 2.9 × 109/L, and a blood platelet count of 118 × 109/L. Laboratory data showed a C-reactive protein level of 319 mg/L, and a coagulation disorder, prothrombin time ratio: 1.33, fibrin degradation product: 32.5 µg/ml, satisfying acute disseminated intravascular coagulation (DIC) criteria according to the Japanese Association for Acute Medical criteria (JAAM criteria) []. Computed tomography indicated a small amount of ascites, edema of the intestinal membrane and retroperitoneum (), and no marked gastrointestinal perforation. We initially suspected diffuse peritonitis with septic shock and DIC, and performed an emergency operation. Intraoperative findings revealed a small amount of cloudy ascites, as well as edema of the intestinal membrane and retroperitoneum, but no gastrointestinal tract perforation or necrosis. To rule out retroperitoneum diseases such as a rupture or leak of ureters, ureterography was performed, but no marked origin of the peritonitis was evident. After abdominal cavity irrigation, drains were placed in the pelvic floor and bilateral subphrenic spaces. Ascites looked serous on the next day of the surgery. He was admitted to the intensive care unit and managed with vasopressor support, mechanical ventilation. He was not diagnosed with acute kidney failure, however, to provide treatment for hypercytokinemia, we started continuous hemodiafiltration (CHDF). Since the causative bacteria species was unknown, CHDF using a polymethylmethacrylate (PMMA) membrane hemofilter was performed as cytokine-absorption therapy without the use of polymyxin B-immobilized fiber column direct hemoperfusion (PMX-DHP). The preoperative blood culture showed group A hemolytic streptococcus (GAS). Because of the isolation of GAS, hypotension, coagulopathy (PT ratio, FDP) and erythematous macular rash, TSLS was confirmed. The postoperative blood culture, intraoperative ascites and urine culture were negative, and only the preoperative blood culture, collected at the previous hospital was positive. For antibiotics, carbapenem antibiotic medication was initially administered as empiric therapy, and cephem-based antibiotic was used after confirming drug sensitivity. Forty-eight hours after starting PMMA-CHDF, vasopressors were reduced from 0.2 to 0.07 µg/kg/min and serum lactate acid levels improved from 3.6 mmol/L to 1.4 mmol/L. He successfully recovered from septic shock after the initiation of cytokine-absorption therapy and responded well to the intensive treatment (). He was intubated for 5 days and discharged from the hospital on postoperative day 25.