What are RASopathies?

The RASopathies are a group of disorders that are due to variations of genes associated with the Ras/MAPK pathway. 

Some RASopathies include the following:

  • Neurofibromatosis type 1 (NF1)
  • Noonan syndrome
  • Noonan syndrome with multiple lentigines
  • Cardiofaciocutaneous (CFC) syndrome
  • Costello syndrome
  • Legius syndrome
  • Capillary malformation-arteriovenous malformation (CM-AVM) syndrome



We characterized the spectrum of dermatologic findings in mutation-positive individuals with cardio-facio-cutaneous (CFC) syndrome. We found that CFC syndrome has a complex dermatologic phenotype with many cutaneous features, some of which allow it to be differentiated from the other Ras/MAPK pathway syndromes. Multiple café au lait macules and papillomata were not identified in our study's CFC cohort, which helps to distinguish CFC from other RASopathies, such as neurofibromatosis type 1 and Costello syndrome. 

Siegel DH, McKenzie J, Frieden IJ, Rauen KA. Dermatological findings in 61 mutation-positive individuals with cardiofaciocutaneous syndrome. Br J Dermatol. 2011 Mar;164(3):521-9. doi: 10.1111/j.1365-2133.2010.10122.x. Epub 2011 Jan 28. PMID: 21062266; PMCID: PMC4063552.


We are grateful to the Costello Syndrome Family Network and all the families who have participated in our research.


Recent RASopathies Publication

Cutaneous mosaic RASopathies associated with rhabdomyosarcoma. Pediatr Blood Cancer. 2022;69(5):e29639.

We presented three novel pediatric cases and 15 previously reported cases that highlight the rare association of RAS-driven birthmarks (such as nevus sebaceous and congenital melanocytic nevi) and rhabdomyosarcoma. This report is the largest cohort of patients with mosaic RASopathies and RAS-driven rhabdomyosarcoma reported together.