Platelet function analyses. Flow cytometric quantification of platelet granule secretion in platelet-rich plasma was stimulated using increasing concentrations of thrombin (0, 0.05, 0.1, 0.2, 0.5, and 1.0 U/ml) (A-B) or collagen (0, 0.25, 0.5, 1, and 2 µg/ml) (C-D). After fixation cells were washed and incubated with fluorescein isothiocyanate-conjugated anti-CD62 (A), phycoerythrin-conjugated anti-CD62 (C), or fluorescein isothiocyanate-conjugated anti-CD63 (B,D). Surface fluorescence was analyzed with a flow cytometer (FACSCalibur; Becton Dickinson). Data are expressed as linear arbitrary units. Analyses were performed with patients’ platelets and platelets from a healthy control. Platelet adenosine triphosphate release in response to collagen was monitored by lumiaggregometry in whole blood (E). Relative luminescence in percent was plotted as a function of time. Analyses were performed with platelets from patient 2 and platelets from a healthy control. Collagen-induced platelet aggregation of platelets from patient 2 and platelets from a healthy control was analyzed using a PAP4-aggregometer (F).