Morphological changes of platelets during the process of platelet aggregation in gray platelet syndrome.

Morphological changes of platelets during the process of platelet aggregation in gray platelet syndrome were observed by means of light microscopy, and scanning and transmission electronmicroscopy. Light microscopic examinations showed normal platelets and slightly enlarged, gray colored ones due to a deficiency in alpha-granules by May-Giemsa stain. At the time of maximum aggregation, normal platelets aggregated completely to form a mass by addition of ADP. On the other hand, patient's platelets only aggregated loosely and each platelet could be recognized separately, resembling primary aggregation of normal platelets. When collagen was added, almost no aggregation was noted in the patient's platelets. Scanning electronmicroscopic examinations revealed the same results as seen by light microscopy. Centralization of platelet organelles and almost complete aggregation and degranulation of platelets were noted immediately after 30 sec and 3-4 min after addition of ADP and collagen on the transmission electronmicrographs in normal platelets, whereas most patient's platelets remained to be unchanged. From these results, we concluded that these morphological changes were consistent with the changes of "release abnormalities" as shown in the functional examinations. Although some relationships between alpha-granule deficiency and functional abnormalities are considered, there is no definitive opinion.