PTPN11 and Noonan syndrome with multiple lentigines: PTPN11, encoding SHP2 protein, is a classic non-receptor protein tyrosine phosphatase, an essential participant in cell signal transduction, regulating cell growth and proliferation.[26] Aberrant expression of PTPN11 can lead to various diseases, for example, PTPN11 is the most common mutant gene in Noonan syndrome (NS) and LEOPARD syndrome (LS),[27] HCM being one of the characteristics of these 2 diseases.