It is caused by mutations in the SPRED1 gene. It is also known as Neurofibromatosis Type 1-like syndrome (NFLS). The syndrome is named after Eric Legius, Professor at the KU Leuven. It is a RASopathy.
The prevalence of Legius syndrome is unknown. Many individuals with this disorder are likely misdiagnosed because the signs and symptoms of Legius syndrome are similar to those of neurofibromatosis type 1.
Nearly all patients show multiple Café au lait spots. Other symptoms may include:
- Freckles in the armpits and/or groin
- Learning disabilities
- Developmental delay
Other signs and symptoms of Legius syndrome may include an abnormally large head (macrocephaly) and unusual facial characteristics. Although most people with Legius syndrome have normal intelligence, some affected individuals have been diagnosed with learning disabilities, attention deficit disorder (ADD), or attention deficit hyperactivity disorder (ADHD).