No reason yet to change diagnostic criteria for Noonan, Costello and cardio-facio-cutaneous syndromes

The clinicogenetic relationship between Noonan syndrome (NS) and Noonan-like syndromes (Costello syndrome (CS), cardio-facio-cutaneous (CFC syndrome) and the disruption of the RAS-ERK pathway makes for a fascinating story that has developed over the past decade, and is still developing. The discovery that the genes causing these syndromes encode proteins that converge on the same metabolic pathway facilitated understanding of the similarities that group these conditions within one family of syndromes.1 Nevertheless, their nosological classification continues to be a challenge. There is general agreement that NS is caused by mutations of PTPN11 (most cases), SOS1 or RAF1 , that CFC syndrome is caused by mutations of BRAF (most cases), MEK1 or MEK2 , and that CS is caused …