Costello syndrome, also called
faciocutaneoskeletal syndrome or
FCS syndrome, is a rare
genetic disorder that affects many parts of the body. It is characterized by delayed development and
mental retardation, distinctive facial features, unusually flexible joints, and loose folds of extra skin, especially on the hands and feet.
Heart abnormalities are common, including a very fast heartbeat (
tachycardia), structural
heart defects, and overgrowth of the
heart muscle (
hypertrophic cardiomyopathy). Infants with Costello syndrome may be large at birth, but grow more slowly than other children and have difficulty feeding. Later in life, people with this condition have relatively
short stature and many have reduced levels of
growth hormones. It is a
RASopathy.