[A novel neurocutaneous syndrome: Legius syndrome. A case report].

Introduction: Legius syndrome is an autosomal dominant disorder caused by the mutation in the SPRED1 gene involving a negative regulator of the RAS-MAPK pathway, similar to neurofibromin and therefore shows some clinical similarities to neurofibromatosis type I (NF1) but less severe. These patients have multiple cafe-au-lait spots, sometimes associated with skin fold freckling, dysmorphic features, lipomas, and mild learning disabilities. However, this syndrome is not associated with neurofibromas, optic gliomas, Lisch nodules or tumor predisposition.

Case Report: We present a 10 months child, without a personal interest history, consulting by hypotonic extremities, cafe-au-lait spots and mild psychomotor difficult. Mother's sister and grandfather have some cafe-au-lait spots. In our patient, NF1 genetic study was negative, but we observe a mutation in the SPRED1 gene, compatible with Legius syndrome. Asymptomatic mother shows the same mutation in SPRED1 gene.

Conclusion: We emphasize the relevance of the differential diagnosis of NF1 with respect to numerous complications to appear, with a better prognosis recently described entity as it is Legius syndrome.