What are the genetic changes related to Sheldon-Hall syndrome ?
Sheldon-Hall syndrome can be caused by mutations in the MYH3, TNNI2, TNNT3, or TPM2 gene. These genes provide instructions for making proteins that are involved in muscle tensing (contraction).  Muscle contraction occurs when thick filaments made of proteins called myosins slide past thin filaments made of proteins called actins. The MYH3 gene provides instructions for making a myosin protein that is normally active only before birth and is important for early development of the muscles.  The process of muscle contraction is controlled (regulated) by other proteins called troponins and tropomyosins, which affect the interaction of myosin and actin. Certain troponin proteins are produced from the TNNI2 and TNNT3 genes. The TPM2 gene provides instructions for making a tropomyosin protein.  Mutations in the MYH3, TNNI2, TNNT3, or TPM2 gene likely interfere with normal muscle development or prevent muscle contractions from being properly controlled, resulting in the contractures and other muscle and skeletal abnormalities associated with Sheldon-Hall syndrome. It is unknown why the contractures mainly affect the hands and feet or how these gene mutations are related to other features of this disorder.