What are the genetic changes related to MYH9-related disorder ?
MYH9-related disorder is caused by mutations in the MYH9 gene. The MYH9 gene provides instructions for making a protein called myosin-9. This protein is one part (subunit) of the myosin IIA protein.  There are three forms of myosin II, called myosin IIA, myosin IIB and myosin IIC. The three forms are found throughout the body and perform similar functions. They play roles in cell movement (cell motility); maintenance of cell shape; and cytokinesis, which is the step in cell division when the fluid surrounding the nucleus (the cytoplasm) divides to form two separate cells. While some cells use more than one type of myosin II, certain blood cells such as platelets and white blood cells (leukocytes) use only myosin IIA.  MYH9 gene mutations that cause MYH9-related disorder typically result in a nonfunctional version of the myosin-9 protein. The nonfunctional protein cannot properly interact with other subunits to form myosin IIA. Platelets and leukocytes, which only use myosin IIA, are most affected by a lack of functional myosin-9. It is thought that a lack of functional myosin IIA leads to the release of large, immature platelets in the bloodstream, resulting in a reduced amount of normal platelets. In leukocytes, the nonfunctional myosin-9 clumps together. These clumps of protein, called inclusion bodies, are a hallmark of MYH9-related disorder and are present in the leukocytes of everyone with this condition.