Key result
Two sisters with lifelong bleeding tendencies were found to have a novel form of dense granule storage pool deficiency, termed empty sack syndrome, where granular membranes are present but contents are reduced.
Case Report (n=2)
Describes a novel form of platelet storage pool disease, termed 'empty sack syndrome', where dense granule membranes are present but lack normal contents.
May inform evaluation of unexplained familial bleeding; extends storage pool deficiency phenotypes but remains hypothesis-generating.
Two sisters with lifelong bleeding tendencies were examined to determine whether their condition was associated with a platelet defect. Their platelet aggregation in response to epinephrine and collagen was abnormal, and the secretion of serotonin and ATP was markedly reduced. The platelet contents of serotonin, ADP, and ATP were all diminished and the ATP:ADP ratio was increased. Direct enumeration by whole-mount and quinacrine-fluorescence techniques demonstrated that the platelets from both sisters had significantly fewer dense granules than controls. These characteristics are similar to an individual with Hermansky-Pudlak syndrome and are consistent with a platelet dense granule deficiency. In contrast, immunofluorescence studies using an antibody against the dense granule membrane protein granulophysin suggested that both sisters had numbers of granules within the normal range. Evaluation by immunoblotting and ELISA indicated the presence of normal levels of granulophysin in the platelets from both sisters; FACS analysis demonstrated the surface expression of granulophysin under conditions of selective dense granule release. These results are consistent with these sisters having a form of dense granule storage pool deficiency where the granular membranes are present but the granules have reduced contents. This observation represents a novel form of storage pool disease which we have termed the empty sack syndrome.
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McNicol et al. (1994) conducted a case report in Lifelong bleeding tendencies / platelet storage pool deficiency (n=2). Platelet storage pool deficiency (empty sack syndrome) vs. Controls was evaluated on Platelet aggregation, secretion, and granule content. Two sisters with lifelong bleeding tendencies were found to have a novel form of dense granule storage pool deficiency, termed empty sack syndrome, where granular membranes are present but contents are reduced.
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