Thrombotic thrombocytopenic purpura (TTP) is a rare, however life threatening syndrome, which is characterized by thrombocytopenia with increased turnover and by loss of peripheral platelets. It belongs to socalled MAHA or MAS disorders (microangiopathic heamolytic syndromes). Combination of microangiopathy, thrombocytopenia and intravascular haemolysis is observed. Clinical picture is also accompanied by fever, alteration of renal functions and variable neurological symptoms which are associated with impaired brain perfusion. The increase of relative amount of highly multimeric (ultra large-UL) von Willebrand factor (vWF) plays a crucial role in the pathogenesis of the disease. The multimer cumulates in the circulation as a result of insufficient concentration of ADAMTS 13 protease that share vWF metalloprotease activity and cleave ULvWF under normal conditions. Treatment option is either substitution of frozen plasma that contains vWF metaloprotease or plasmapheresis that is obviously more effective and has a potential to eliminate autoantibodies against ADAMTS 13 protease, which usually cause the functional ADAMTS 13 protease deficit. TTP also occurs in patients with systemic connective tissue diseases, mostly with SLE. The authors describe 3 patients with SLE that developed TTP. SLE was defined in all patients according to the ARA criteria. All three patients were hospitalized for rather acute onset of haemolytic anemia, thrombocytopenia and neurological symptoms. They were treated with plasmapheresis, and furthermore with high doses of frozen plasma and intensive immunosuppressive agents. One patient flared with the necessity of rehospitalization, and one died of multiorgan failure during the attack of TTP. TTP may accompany systemic connective tissue diseases as a secondary syndrome or can develop after the treatment with some drugs. In the case of acute decrease of blood elements, particularly thrombocytes, it is necessary to be aware of this possibility because unrecognized and insufficiently treated disease results very often in death.

        Key words: SLE, thrombotic thrombocytopenic purpura