Background and Objectives. May-Hegglin anomaly

penia. The differentiation of MHA from SBS is based on subtle differences in the ultrastructural features of the Dhle-like bodies. 1,2 The MHA-SBS genetic defect has been recently mapped on the long arm of chromosome 22 3 and then identified in the gene (MYH9) encoding the heavy chain of non-muscle myosin IIA (NMMHCIIA) . MYH9 mutations are associated with two other macrothrombocytopenic syndromes: Fechtner syndrome, 7 characterized by nephritis, sensorineural hearing loss, cataract and polymorphonuclear inclusion bodies, and Epstein syndrome, 8-10 differing from Fechtner syndrome by the absence of cataract and Dhle-like bodies. Vertebrates possess two isoforms of NMMHC-II, which are widely and differentially expressed in tissues and have overlapping but distinct intracellular localizations. 11 Only NMMHC-IIA is expressed in human platelets and leukocytes. In normal subjects it has a diffuse and homogeneous distribution in leukocyte cytoplasm and platelets, while in p