A 75-year-old man, treated for arterial hypertension, was diagnosed with stage I colon cancer. He was submitted to colon resection and one week later developed an infectious peritonitis, that was controlled with systemic broad spectrum antibiotics. One month after surgery, he presents to his general practitioner (GP) with daily fever (>38 C), weight loss, and progressive asthenia. Physical examination was not remarkable. The GP suspected infection and prescribed oral antibiotics. Blood tests showed pancytopenia (Table 2) with negative serology for HIV, B and C hepatitis, EBV, CMV, Rickettsia conorii, Leptospira, Borrelia burgdorferi, and Salmonella typhi. Active tuberculosis infection was also excluded. The condition extended for 3 months, with no response to treatment and clinical deterioration with unremitting fever. The patient was admitted to hospital where he began broad spectrum antibiotics (piperacillin-tazobactam 4,5 g, t.i.d.) and prednisolone 40 mg/m2. Repeated serologies and bacteriologic cultures were inconclusive. A thoracoabdominal CT scan showed a soft spleen enlargement (14,5 cm x 6 cm). The main clinical suspicion was an occult infection. Blood tests showed persistent and worsening pancytopenia, with hepatic cytolysis and cholestasis, elevated ferritin, and triglycerides (Table 2). A bone marrow biopsy was performed presenting signs of phagocytosis of blood elements. The diagnosis of HPS was then made (Figure 1). Despite the diagnosis, his clinical status worsened and rapidly evolved to multiorgan failure (MOF) with hepatic, respiratory, and cardiac dysfunction. He died 10 days after admission.