Platelets contain three groups of secretory organelles: α-granules, δ-granules (“dense bodies”), and lysosomes. Inherited defects of platelet granules (SPD, storage pool deficiency) can affect α-granules, δ-granules, or both (combined). α- or δ-granules may be reduced or absent or may have a defect in releasing their content. Depending on the nature of the underlying disorder, platelet count, size (macro−/microthrombocytopenia), and morphology can also be altered. In addition to the classic defects (Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, and Griscelli syndrome), which often affect proteins directly involved in granule biogenesis, a group of granule defects has been identified in recent years that are associated with genetically altered hematopoietic transcription factors.