Hemophagocytic lymfohistiocytosis (HLH) is rare, life-threatening condition, characterized by excessive activation of immune system with subsequent proinflammatory state resulting in multiorgan failure. Most frequently, it appears in infancy as a primary disorder caused by mutation of immune-regulatory genes. Increasingly, HLH is being diagnosed as a secondary - adult - form, which occurs as a result of aberrant immune response. Viral or bacterial systemic infections, malignancy with a predominance of lymphoproliferative disorders and autoimmune diseases are the most common triggers. Early diagnosis and initiation of therapy is crucial and increase the chance for recovery. HLH is usually presented as multisystem febrile illness, where an extensive differential diagnosis is needed. Diagnosis of HLH is defined by a combination of clinical and laboratory findings, eventually by a proof of specific mutation. The basic mechanism of therapy is an interruption of aberrant immune response by destruction and suppression of T-lymphocytes function. This is mostly achieved by corticosteroid and etoposide therapy. This review summarizes pathophysiology, diagnostics and therapy of HLH. Furthermore, a case-report of 22-years old patient with secondary HLH being manifested predominantly with acute respiratory failure is presented.Key words: acute respiratory failure - hemophagocytic lymphohistiocytosis - HLH-94 - macrophage activation syndrome - MODS.