LAUSR

A 52-year-old woman presented to our hospital with postmenopausal osteoporosis and coronary atherosclerosis. Her full blood count showed a platelet count of 73 9 10/l. A blood film of EDTA-anticoagulated blood showed platelet clumping and platelet satellitism around both neutrophils and lymphocytes. More importantly, platelet phagocytosis was noted not only in neutrophils and monocytes, but also in lymphocytes (image). Platelet satellitism was absent in both citrated and heparinised blood specimens. However, platelet clumping was more obvious in heparinised blood and platelet phagocytosis by neutrophils was occasionally seen in citrated blood. A finger-prick blood film showed no platelet satellitism or phagocytosis. The corrected platelet count was 158 9 10/l. Flow cytometry for platelet-associated immunoglobulin was strongly positive with platelets from EDTA-anticoagulated blood but not with those from citrated blood. Platelet phagocytosis is an in vitro phenomenon usually involving neutrophils and occasionally monocytes. It is quite uncommon for lymphocytes, which have usually been thought to lack phagocytic ability. We postulate that the phenomenon of platelet satellitism and phagocytosis in this patient relates to immunoglobulin bound to platelets in the presence of EDTA.