Legius Syndrome and its Relationship with Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is the most common disorder characterized by multiple cafe-au-lait macules. Most individuals with this autosomal dominant disorder also have other features, such as skinfold freckling, iris Lisch nodules and benign or malignant peripheral nerve sheath tumours. Legius syndrome is a less frequent autosomal dominant disorder with similar multiple cafe-au-lait macules and skinfold freckling. Legius syndrome is not characterized by an increased risk of tumours, and a correct diagnosis is important. In young children with a sporadic form of multiple cafe-au-lait macules with or without freckling and no other manifestations of NF1 these 2 conditions cannot be differentiated based on clinical examination. Molecular analysis of the NF1 and SPRED1 genes is usually needed to differentiate the 2 conditions. Other less frequent conditions with cafe-au-lait macules are Noonan syndrome with multiple lentigines, constitutional mismatch repair deficiency and McCune-Albright syndrome.