GFI1B and Thrombocytopenia: A pale phenotype of large platelets is indicative of a deficiency of α-granules, as observed for the classical GPS caused by pathogenic NBEAL-2-variants, GFI1b-related thrombocytopenia caused by GFI1b-mutations, and the arthrogryposis—renal dysfunction—cholestasis (ARC)-syndrome caused by pathogenic gene variants in VPS33B or VIPAS39. GATA1-related diseases are typically characterized by a subpopulation of large and vacuolated platelets, and they could be associated with a decreased number of α-granules or a combined α-/δ-storage pool defect [26,27].