Alterations of the complement system in patients with catastrophic antiphospholipid syndrome

Aim. To investigate alterations of the complement system in patients with catastrophic antiphospholipid syndrome (CAPS). Subjects and methods. Four patients (2 men aged 23 and 40 years and 2 women aged 39 and 58 years) diagnosed as having CAPS, including 3 patients with systemic lupus erythematosus and secondary antiphospholipid syndrome (APS) and 1 patient with primary APS, were examined. The activity of the complement components C1-C5 and total hemolytic activity were determined in all the patients at the moment of an acute episode and in 1 patient after treatment. Results. The activity of the studied complement components and total hemolytic complement activity proved to be significantly decreased in all the patients. That of complement components recovered after treatment using fresh frozen plasma. The possibility and mechanisms of complement system activation in the patients with CAPS are discussed. Conclusion. The preliminary results obtained by the examination of few cases may lead to the conclusion that the complement system may be involved in the development of CAPS.