VWF and thrombotic thrombocytopenic purpura: Currently, ADAMTS13 activity testing in plasma is the key laboratory hallmark for the differential diagnosis of TMAs, because values below 10% of normal (i.e., ADAMTS13 severe deficiency) are diagnostic for TTP and support the initiation and continuation of therapy with plasma exchange (PEX) and immunosuppressors, nowadays with the adjunct use of the anti-VWF nanobody caplacizumab [19].