Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Gray platelet syndrome ?
    ### Response:
    Gray platelet syndrome (GPS) is a rare inherited bleeding disorder characterized by platelets that have a gray appearance, severe thrombocytopenia, myelofibrosis, and splenomegaly. About 60 cases from various populations around the world have been described in the literature to date.
    