The clinical picture of systemic lupus and antiphospholipid syndrome is remarkably varied and disease manifestations are commonly very heterogeneous. Relatively often both diseases are associated with severe, acute and life threatening manifestations, which places demands on the knowledge of differential diagnostics and experience of the physicians. This article deals with the serious and mostly acute impairment of cardiovascular, respiratory, renal, gastrointestinal, hematopoietic or nervous systems, briefly discusses the acute pregnancy complication and summarizes the basic therapeutic option. It emphasizes the role of both, sometimes inseparable, diseases in differential diagnosis of acute symptoms in internal medicine.Key words: clinical symptoms - diagnostics - live threatening manifestations - lupus erythematosus - systemic antiphospholipid syndrome - therapy.