Platelets and coagulation in patients with familial hypercholesterolemia (type IIa).

Seventeen subjects with hypercholesterolemia (type IIa) were compared with 11 normocholesterolemic family members (controls) with similar dietary habits. The type IIa subjects had a shorter bleeding time. Beta-thromboglobulin in plasma and thromboxane B2 and malondialdehyde released from platelets before and after stimulation with collagen or thrombin were similar. No differences in platelet sensitivity to adenosine diphosphate, thrombin or collagen were observed. Gel-filtered platelets from type IIa subjects had a tendency to spontaneous aggregation and lower procoagulant activity. Platelet sensitivity to prostacyclin was slightly higher in type IIa subjects. No differences in a series of coagulation parameters were observed between the groups. This study has shown some deviations from normal in platelets from subjects with familial hypercholesterolemia. These changes may contribute to the increased tendency to occlusive vascular diseases in such subjects.