To cite this article: Morel-Kopp M-C, Mullier F, Gkalea V, Bakchoul T, Minet V, Elalamy I, Ward CM, for the Subcommittee on Platelet Immunology. Heparin-induced multi-electrode aggregometry method for heparin-induced thrombocytopenia testing: communication from the SSC of the ISTH.

No abstract

Rare gain-of-function mutations within the ITGA2B or ITGB3 genes have been recognized to cause macrothrombocytopenia (MTP). Here we report three new families with autosomal dominant (AD) MTP, two harboring the same mutation of ITGA2B, αIIbR995W, and a third family with an ITGB3 mutation, β3D723H. In silico analysis shows how the two mutated amino acids directly modify the salt bridge linking the intra-cytoplasmic part of αIIb to β3 of the integrin αIIbβ3. For all affected patients, the bleeding syndrome and MTP was mild to moderate. Platelet aggregation tended to be reduced but not absent. Electron microscopy associated with a morphometric analysis revealed large round platelets; a feature being the presence of abnormal large α-granules with some giant forms showing signs of fusion. Analysis of the maturation and development of megakaryocytes reveal no defect in their early maturation but abnormal proplatelet formation was observed with increased size of the tips. Interestingly, this study revealed that in addition to the classical phenotype of patients with αIIbβ3 intracytoplasmic mutations there is an abnormal maturation of α-granules. It is now necessary to determine if this feature is a characteristic of all mutations disturbing the αIIb R995/β3 D723 salt bridge.

MYH9-related disease (MYH9-RD) is an inherited rare autosomal dominant macrothrombocytopenia. Patients with MYH9-RD have giant platelets and leukocyte inclusion bodies caused by mutations in the MYH9 gene encoding the non-muscle myosin heavy chain II-A. Before identification of the causative gene, patients were diagnosed as Epstein or Fechtner or Sebastian syndromes or May-Hegglin anomaly. As with other inherited thrombocytopenias, the risk of increased bleeding during perioperative period or delivery is a major concern. We report here the first successful cesarean delivery of a woman with MYH9-RD treated with eltrombopag during the last month of pregnancy.