Moreover, its genetic origin may not be suspected if there is no family history, either because it is recessively-inherited, or because, as documented in up to 40% of individuals with MYH9-RD (MYH9-related disease) it is due to molecular defects with incomplete penetrance or that appear “de novo” in the patient Fundamentals that inform the diagnosis of inherited thrombocytopenias include platelet size evaluation on the peripheral blood smear and a proper physical examination that points toward a syndrome. The gene discussed is MYH9; the disease is Thrombocytopenia.