Noun
Costello syndrome (uncountable)
A rare genetic disorder characterized by delayed development and intellectual disabilities, distinctive facial features, unusually flexible joints, and loose folds of extra skin, especially on the hands and feet.
Henry’s DNA was sent for exome sequencing and, in less than a week, was diagnosed with Costello syndrome – a rare disease that can cause a range of health problems and lead to an increased risk of childhood cancer. Source: Internet