Summary

About 60% of patients diagnosed with acute thrombotic thrombocytopenicpurpura (TTP) display a severe ADAMTS13deficiency. Recently, Raife et al. concluded from a small caseseries, that factor V Leiden (FVL) might constitute a risk factorfor acute thrombotic microangiopathy (TMA) without severeADAMTS13 deficiency. Therefore, we determined ADAMTS13activity and FVL carrier-ship in 256 consecutive patients presentingwith various forms of acute TMA, including patients diagnosedwith TTP or hemolytic-uremic syndrome (HUS). Theoverall prevalence of FVL was 8.2% (6.25% among patients diagnosed with TTP, and 9% among those with HUS) concordantwith the FVL prevalence reported in Europe. FVL was present in9.9% of patients with ADAMTS13 activity <10% and in 9.7% ofthose with normal ADAMTS13 activity (>50%). We concludethat FVL is not more prevalent inTMA patients without as comparedto those with severe ADAMTS13 deficiency. The prevalenceof FVL carriers in certain HUS subgroups (HUS withADAMTS13 activity >50%) reaching 12.3% suggests that a contributoryrole of FVL in the pathogenesis of defined forms ofHUS needs further study.