Platelet function and lipoprotein levels after plasma-exchange in patients with familial hypercholesterolaemia.

1. Repeated plasma exchange was carried out on three young patients with severe familial hypercholesterolaemia. There was a 3 week interval between each exchange. After a single exchange, plasma cholesterol, apolipoprotein B and low density lipoprotein-cholesterol levels decreased markedly, but pre-exchange levels were not achieved within 2 weeks. High density lipoprotein-cholesterol and apolipoprotein A-I levels also fell but returned to the original concentration after only 5 days. 2. Platelet aggregation and [14C]serotonin release were increased in all three patients and dropped by 20% and 13% respectively after a single plasma exchange. Platelet function in vitro returned to pre-exchange levels with similar kinetics to that observed with the low density lipoprotein concentration. On removal of 100 g of plasma cholesterol, after repeated exchanges, low density lipoprotein concentration and platelet function were significantly decreased in comparison with values before initiation of plasma exchange. In addition there was a marked regression of xanthoma in all three patients. 3. Since this procedure is instrumental in achieving a negative cholesterol balance as well as inhibiting hypersensitive platelets, it may well result in a downgrading of the atherosclerotic risk.