Pseudo grey platelet syndrome--grey platelets due to degranulation in blood collected into EDTA

We have studied a woman with a history of mild bruising and bleeding, with a normal platelet count and normal clotting factors, who had platelets that appeared grey when stained and viewed under the microscope. Unlike the grey platelet syndrome, the abnormality was only evident when blood had been collected into EDTA and not when citrate or heparin was used as anticoagulant. This 'pseudo grey platelet syndrome' was associated with platelet dense body and alpha granule secretion with no aggregation and occurred on removal of extracellular Ca2+. We discovered that a plasma factor was responsible which could be an immunoglobulin but which is clearly different from the EDTA-sensitive antibodies which cause platelet aggregation and agglutination. We were not able to demonstrate a relationship between the mild bleeding tendency and the in vitro abnormality.