Legius syndrome

Legius syndrome, also known as neurofibromatosis type 1-like syndrome (NF1-like syndrome), is a rare autosomal dominant genetic disorder caused by pathogenic variants in the SPRED1 gene located on chromosome 15q14. SPRED1 encodes a negative regulator of the RAS-MAPK signaling pathway, and loss-of-function mutations lead to dysregulation of this critical cell signaling cascade. Legius syndrome shares several clinical features with neurofibromatosis type 1 (NF1) but is considered a distinct and generally milder condition. The hallmark feature of Legius syndrome is the presence of multiple café-au-lait macules (flat, hyperpigmented skin patches), which typically appear in early childhood. Axillary and inguinal freckling (skinfold freckling) is also commonly observed. Some individuals may have a macrocephalic head circumference, mild learning difficulties, or attention-deficit issues. Importantly, Legius syndrome is distinguished from NF1 by the absence of neurofibromas, optic pathway gliomas, Lisch nodules (iris hamartomas), and osseous lesions that are characteristic of NF1. The condition primarily affects the skin and may have mild neurodevelopmental implications, but it does not carry the tumor predisposition risks associated with NF1. There is currently no specific or curative treatment for Legius syndrome. Management is primarily supportive and involves regular clinical monitoring, dermatological assessment of café-au-lait macules, developmental and educational support for children with learning difficulties, and genetic counseling for affected families. Accurate molecular diagnosis through SPRED1 gene testing is important to differentiate Legius syndrome from NF1, as the prognosis and surveillance recommendations differ significantly between the two conditions. Overall, the long-term outlook for individuals with Legius syndrome is generally favorable compared to NF1.

Common questions about Legius syndrome