PTPN11 and Leigh syndrome: LEOPARD syndrome (LS), a type of RAS/MAPK pathway disorder (RASopathies), is a malformation syndrome named by Gorlin in 1969 and an acronym for lentigines, electrocardiogram (ECG) conduction abnormalities, ocular hypertelorism, pulmonic stenosis, abnormal genitalia, retardation of growth, and deafness.1 About 85% of patients with LS show variants in exons 7, 12, and 13 of the PTPN11 gene.2 PTPN11 encodes a Src homology region 2 (SH2) domain–containing tyrosine phosphatase 2 or SHP2 protein.