[May-Hegglin anomaly: past and present--novel diagnostic test and new concept of the disease].

May-Hegglin anomaly(MHA) is the prototype of the autosomal dominant macrothrombocytopenia with leukocyte inclusion bodies/MYH9 disorders that result from mutations in MYH9, the gene for nonmuscle myosin heavy chain-IIA(NMMHC-IIA). Others include Sebastian(SBS), Fechtner(FTNS), and Epstein (EPS) syndromes. Clear phenotype-genotype relationships have not been found; however, patients with an MYH9 head domain mutation tend to develop Alport manifestation more frequently than those with a rod mutation. The hallmark of MYH9 disorders is the presence of granulocyte inclusion bodies. We revealed that mutant NMMHC-IIA was present and sequestered only in inclusion bodies within neutrophils, diffusely distributed throughout lymphocyte cytoplasm, sparsely localized on a diffuse cytoplasmic background in monocytes, and uniformly distributed at diminished levels only in large platelets. We showed the differential expression of mutant NMMHC-IIA, and postulated that cell-specific regulation mechanisms function in MYH9 disorders.