Hereditary thrombocytopenias are a heterogeneous group of extremely rare diseases characterized by a reduced number of blood platelets and by bleeding tendency of variable severity. Some of these diseases are exclusive to platelets, while in others the pathology extends to other cell types. Although rare, hereditary thrombocytopenias should be considered in the diagnosis. Hereditary thrombocytopenias have been classified into three groups depending on platelet volume. Hereditary thrombocytopenias with giant platelets form one of these groups. About fourteen clinical entities of inherited giant platelet disorders have been described. Bernard-Soulier syndrome, grey platelet syndrome andMay-Hegglin anomaly are the most common giant platelet thrombocytopenias.May-Hegglin anomaly is condition characterized by the triad of thrombocytopenia, giant platelets, and pale-blue inclusions in leukocytes. May-Hegglin anomaly has an autosomal-dominant mode of inheritance.We described clinical and laboratory features of three adult women from one family with recently diagnosedMay-Hegglin anomaly. Described cases are probably the first observed cases of May-Hegglin anomaly in the Czech lands.

        Key words: inherited thrombocytopenias, May-Hegglin anomaly, platelets.