Seven genes (PTPN11, SOS1,KRAS, RAF1, BRAF,SHOC2 and MEK1, alias MAP2K1) have beencausally related to NS and closely related conditions (including LEOPARDsyndrome) and clinically related disorders (e.g. neurofibromatosis type 1) [2]. This evidence concerns the gene PTPN11 and neurofibromatosis type 1.