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Giant platelets with abnormal surface glycoproteins: a new familial disorder associated with mitral valve
P S Becker1, L A Clavell, D S Beardsley
1Cancer Center, University of Massachusetts Medical Center, Worcester, USA.
Purpose:
To study the platelets from a family with a new form of inherited giant platelet disorder.
Patients And Methods:
Two siblings exhibited a hemorrhagic disorder characterized by moderate thrombocytopenia, giant platelets, and markedly prolonged bleeding time. The parents had no discernible platelet defect. Both children also developed mitral regurgitation requiring medication, and one underwent surgical replacement at the age of 3 years.
Results:
The mean platelet size was greater than 20 microm3. Direct measurements of the two major axes of each of 12 platelets on electron micrographs revealed a range of 2x4 to 4x6 microm. Electron microscopy did not demonstrate any abnormality of granule content. The platelets agglutinated normally with ristocetin and aggregated normally with collagen. However, the aggregation was slightly slower than normal with ADP, epinephrine, and Na arachidonate. Two-dimensional unreduced versus reduced SDS-polyacrylamide gel electrophoresis of surface radioiodinated platelet glycoproteins revealed absence of proteins Ia, Ic, and IIa in both affected children, whereas GP Ib, IIb, and IIIa appeared normal. The 2D gels of platelet glycoproteins from both parents were identical to controls. Western blots demonstrated that GP Ic, Ic', Ib, and Ia/IIa were present.
Conclusions:
This disorder represents a new syndrome of thrombocytopenia with giant platelets distinct from Bernard-Soulier, Montreal giant platelets, Swiss cheese platelets, May-Hegglin anomaly, and other previously described syndromes.