Trombotische microangiopathie: trombocytopenie en hemolytische anemie

Thrombotic microangiopathy is an acute and severe syndrome characterised by a combination of thrombocytopenia, haemolytic anaemia with a negative direct antiglobulin test, and fragmentocytes in the blood smear. The condition can be idiopathic but can also be caused by various underlying diseases. The main causes are thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome. By measuring the von Willebrand factor cleaving protease activity, it now appears possible to distinguish between the different causes of thrombotic microangiopathy, although the sensitivity and specificity of this measurement still need to be clarified. In patients with haemolytic uraemic syndrome without preceding diarrhoea, one should search for infectious foci outside the gastrointestinal tract, using a polymerase-chain reaction to detect the two different verotoxin genes where necessary. Plasmapheresis treatment has reduced the fatality rate amongst patients with thrombotic thrombocytopenic purpura from 90% to 10-25%. Since patients benefit most from rapid institution of treatment, yet the diagnostics currently take several days, the recommendation in case of doubt regarding the original diagnosis is to apply initial plasma exchange therapy to all patients with thrombotic microangiopathy.