VWF multimeric structure before and after DDAVP administration in 4 patients with type 2A VWD. Plasma of healthy controls (NP) and of 4 patients with type 2A VWD with mutations S506L (A), R1597W (B), G1629R (C), and V1665E (D) before and 30 minutes, 1 hour, 2 hours, and 4 hours after DDAVP administration are shown (from left to right). In the 2 patients with the first group of type 2A defects (S1506L and V1665E), there were no changes in the proportion of the high-molecular–weight multimers after DDAVP or in the prolonged BT (more than 30 minutes) and low VWF:RCo/Ag ratios (less than 0.30) observed at baseline (Table 2). Conversely, in the 2 patients with the second group of type 2A defects (R1597W and G1629R), a transient appearance of high-molecular–weight multimers is observed after DDAVP administration and transient normalization (6 and 10 minutes) of the prolonged BT (more than 30 minutes at baseline). The low VWF:RCo/Ag ratios (less than 0.30) observed at baseline did not change appreciably (Table 2).