Family study. (A) Pedigree of patient M. □ indicates unaffected male; ▪, affected male; ○, unaffected female; •, affected female; / indicates deceased. Tyr and Cys, respectively, represent tyrosine and cysteine at residue 1584 in VWF, determined by genotype analysis. (B) Multimer analysis showing proteolysis of VWF from each family member. T = 0 hours shows the multimer profile of the VWF in each cryoprecipitate before incubation with cryodepeleted plasma containing ADAMTS13. Incubations were done for fixed time intervals according to the presence (4 hours) and absence (8 hours) of ristocetin. The extent of proteolysis is greater in the case of lanes M and 2:3 both in the presence and absence of ristocetin. (C) Densitometric scans of the lanes in panel B. Each panel corresponds with one lane. In both the presence and absence of ristocetin, the plasma VWF from patient M and sibling 2:3 shows greater proteolysis than that of the other individuals tested. In all cases, proteolysis is accompanied by a quantitative increase in the triplet bands. The horizontal axis is optical density: 0 = black, 500 = white.