A bone marrow puncture-biopsy was performed. Activated macrophages with hemophagocytosis were found (figure 1), which together with the clinical and analytical data (bicytopenia, and coagulopathy with hypofibrinogenemia, and afterwards a ferritin of 190594 μg/L and triglycerides of 677 mg/dL) confirmed the HFS diagnosis. Specific treatment for this syndrome was started, following Hemophagocytic Lymphohistiocytosis (HLH) 2004 guidelines. She had a very good response, and at forth day from admission she was extubated to non invasive ventilation using a full-face mask. A progressive analytical normalization was observed and she was discharged after 12 days in PICU, without any sequelae.