Legius syndrome (LS) is an autosomal dominant condition characterized by cafe au lait spots.^[1]

• It was first described in 2007 and is often mistaken for Neurofibromatosis type I (NF-1).
• The syndrome is named after Eric Legius, Professor at the Katholieke Universiteit Leuven|Catholic University of Leuven.

It is caused by mutations in the SPRED1 gene.^[2][3][4]

Neurofibromatosis type 1

• Features common in neurofibromatosis – lisch nodules, bone abnormalities, neurofibromas, optic nerve gliomas and malignant peripheral nerve sheath tumors – are absent in this condition.

• The similarity of symptoms stem from the fact that the different genes affected in the two syndromes code for proteins that carry out a similar task in the same reaction pathway.

• A genetic test is often the only way to make sure a person has Legius syndrome and not NF-1.

• Because of this difference, Legius syndrome is often seen as the less severe of the two syndromes.

• Learning disabilities
• Developmental delay^[5]

• Nearly all patients show multiple café au lait spots.
• Freckles in the armpits and/or groin
• Lipomas

• Macrocephaly

• Developmental delay^[5]

• ADHD

• Genetic testing is necessary to identify the syndrome.
• The test checks for loss of function mutations in the SPRED1 gene.