[Autosomal dominant macrothrombocytopenia with leukocyte inclusion bodies and MYH9 disorders]

May-Hegglin anomaly (MHA) is the prototype of 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, Fechtner, and Epstein syndromes. A clear phenotype-genotype relationship has not been found; however, patients with an MYH9 head domain mutation tend to develop Alport manifestations more frequently than those with a rod domain mutation. Patients initially diagnosed with MHA and/or Sebastian syndrome can subsequently develop nephritis, deafness, and/or cataracts. Thus, the development of Alport manifestations should be monitored by careful follow-up.