GP1BB and Macrothrombocytopenia: In fact, these GPIbβΔIC–/– mice, while presenting macrothrombocytopenia typical of the BSS phenotype, expressed approximately 20% of the GPIb-IX complex on the platelet surface and showed a significantly milder bleeding tendency with respect to the GPIbβ–/– knock-out mice, which expressed approximately 3% of the complex and had a severe bleeding phenotype [11].