Definition

A rare genetic condition marked by flat brown spots on the skin. The number of brown spots on the skin tends to increase throughout childhood. Other signs and symptoms include an abnormally large head, unusual facial features, and freckling in the armpits and groin. People with this syndrome may have mild learning and developmental delays. Legius syndrome is a type of disease called a RASopathy that is caused by mutations (changes) in the SPRED1 gene. This gene makes a protein involved in a cell signaling pathway that controls many important cell functions. Also called neurofibromatosis type 1-like syndrome.