Thrombotic events in MYH9 gene-related autosomal macrothrombocytopenias (old May-Hegglin, Sebastian, Fechtner and Epstein syndromes).

Congenital macrothrombocytopenia are a group of disorders which may be due to mutations in the MYH9 gene. This gene linked to chromosome 22 encodes for the nonmuscle heavy chain IIA that is expressed in platelets and in other tissues. In the past these disorders were known as May-Hegglin anomaly, Sebastian, Fechtner and Epstein syndromes. The main common feature is the presence of thrombocytopenia with large platelets. The evaluation of all reported cases indicates that thrombotic events appear to occur only in patients with May Hegglin variants. Whether this is due to the higher prevalence of this variant as compared with the others or to a specific difference is still unknown. However, the occurrence of thrombotic events in only one of these conditions may be used as a new tentative differentiability feature.