Definition

A rare genetic disorder that is caused by a mutation (change) in the HRAS gene. Costello syndrome is marked by shorter-than-average height, unusual facial features, extra folds of skin (especially on the neck, hands, and feet), loose joints, heart problems, and learning and developmental delays. People with Costello syndrome may develop small, non-cancerous wart-like growths called papillomas around the nose, mouth, or anus. They also have an increased risk of developing certain types of cancer, especially rhabdomyosarcoma (a type of soft tissue tumor) and neuroblastoma (cancer that forms from immature nerve cells).