In this case-report, a young female patient presented with a systemic inflammatory disease, accompanied by an extremely elevated ferritin blood level (Hyperferritinemia).The combination of high fever with extremely elevated ferritin level is considered to be a medical emergency being associated with the following four life threating conditions: Adult-onset Still's disease, catastrophic antiphospholipid syndrome, septic shock and macrophage activating syndrome. These conditions were recently bundled under the umbrella term of Hyperferritinemia Syndrome. During the patient's hospitalization, after empiric board spectrum antibiotics did not appear to improve the patient's condition, she was diagnosed with Adult-onset Still's disease and treated with steroids and methotrexate, resulting in gradual clinical improvement. This patient exemplifies a diagnostic challenge, recurring in the patients' milieu of internal medicine departments. Therefore, we discuss the differential diagnosis of Hyperferritinemia syndrome and treatment options for refectory adult's Still disease.