CED is caused by mutations in TGFB1 which encodes transforming growth factor beta-1 protein. This protein helps control the growth and proliferation of cells, the process by which the cells mature and begin to specify (differentiate), cell movement, and cell directed self-destruction (apoptosis). The specific protein plays a huge role during prenatal development in the formation of blood vessels, the regulation of muscle tissue and body fat development, wound healing, and immune system function. The protein is most abundant in skeletal tissue and the extracellular matrix that provides structural support and nutrients to the surrounding cells.
Normally, TGFB1 is inactive until a chemical signal is sent to turn it on. TGFB1 mutations that cause CED result in the gene being always turned on and active. This leads to increased bone density and decreased fat and muscle tissue, contributing to the symptoms listed above. Most individuals with CED have a TGFB1 mutation identified on molecular genetic testing, but some affected individuals do not.
CED is inherited as an autosomal dominant condition. This occurs when only a single copy of the mutated gene is needed to cause a specific disorder. The altered gene can be inherited from either parent, or can be a new mutation in the affected individual. The risk of transmitting the disease to the offspring of an affected parent is 50%, and is the same for males and females. Rarely, the disease can come from a spontaneous genetic mutation in the egg or sperm cell. In these people, the disease isn’t inherited from the one of the parents, but the individual can still pass it to their offspring.