Alpha-delta platelet storage pool deficiency in three generations

Alpha-Delta platelet storage pool deficiency (αδ SPD) is a rare inherited bleeding disorder affecting both males and females, occurring in families, as well as sporadically. Patient platelets in most cases are moderately deficient in both α granules and dense bodies. Only one patient has been severely deficient in both organelles. The present study is the first to document a severe decrease in both platelet α granules and dense bodies in four members in three generations of the same family. Efforts to differentiate this disorder from other hypogranular platelets syndromes in the present investigation suggested that the α granules and dense bodies become connected to channels of the open canalicular system (OCS) and lose their contents to the exterior without prior activation of the cells. In contrast, α granule formation in the white platelet syndrome is too slow, and cells leave the bone marrow still in the process of producing organelles. Gray platelet syndrome platelets can make α granules, but their enclosing membranes are unable to retain stored products. As a result, the organelles lose their contents to surrounding cytoplasm in megakaryocytes and platelets, not selectively through the demarcation system channels and OCS channels. Thus, the pathogenesis of αδ SPD is unique.