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Large platelets have a diameter greater than 4 microns.  Giant platelets have a diameter greater than 7 microns (larger than a normal red blood cell).  Large platelets can be seen when platelet turnover is increased (as in immune thrombocytopenic purpura).  They may also be present in myeloproliferative neoplasms, myelodysplasia, and some congenital thrombocytopenia syndromes, including Bernard-Soulier syndrome and MYH9-related disorders.  Giant platelets may fall outside the upper size threshold for platelets on hematology analyzers.  If sufficient numbers of giant platelets are present,  the automated platelet count may be falsely decreased.