Microangiopathic haemolytic anaemia in metastasizing malignant tumours is not associated with a severe deficiency of the von Willebrand factor-cleaving protease

Complete deficiency of von Willebrand factor-cleaving protease (VWF-cp) has recently been identified as a pathogenetically important factor for thrombotic thrombocytopenic purpura (TTP). Microangiopathic haemolytic anaemia (MAHA) with thrombocytopenia in patients with metastasizing neoplasms is clinically similar to TTP, however, the pathogenesis of the condition is unclear. Partial deficiency of VWF-cp in metastasizing malignancy has recently been reported in patients without MAHA, Our study shows normal or subnormal VWF-cp activity in four patients with metastasizing neoplasia-associated MAHA but, in contrast to classical TTP, no complete deficiency of VWF-cp despite the full clinical picture of MAHA.