The gray platelet syndrome (GPS) is a rare inherited disorder of the megakaryocyte (MK)
lineage. Thrombocytopenia and enlarged platelets are associated with a specific absence of
α-granules and their contents. GPS patients exhibit much heterogeneity both in bleeding
severity and in their response to platelet function testing. A unique feature is that proteins
endogenously synthesised by megakaryocytes (MK) or endocytosed by MK or platelets fail
to enter into the secretable storage pools that characterise α-granules of normal platelets …