【Introduction】LEOPARD syndrome (LS) is a complex of multisystemic diseases characterized by profuse lentigines, hypertrophic cardiomyopathy and pulmonary stenosis, combined with growth retardation and deafness. Recently, in LS patients, mutations have been reported in PTPN11, a gene which has been indicated as the responsible gene for Noonan syndrome (NS). Marfan syndrome (MFS) is an autosomal dominant disorder of the connective tissues, mainly affecting the cardiovascular, ocular and skeletal systems. Mutations in the FBN1 gene are reported to be responsible for MFS in more than 90% of the cases. In the current study, we report a patient who demonstrated characteristics of both LS and MFS, and in whom mutations were identified in both the PTPN11 gene and FBN1 gene.【Case】The patient was a 12-year-old boy at first visit with MFS family histroy. He was born at 40 weeks gestation, with a birth weight of 3500 g. Multiple lentigines, failure to thrive and developmental delay were initially observed. Short stature, scoliosis, joint laxity and cubitus valgus were also existed. Dilation of the aorta and hypertrophic obstructive cardiomyopathy were found in the cardiac system. The patient later died at age 29 due to a dissecting aortic aneurysm. Genetic screening of the PTPN11 gene disclosed a missense heterozygous mutation Tyr279Cys in exon7, and a nonsense heterozygous mutation Cys488Stop in exon11 of the FBN1 gene.【Discussion】This is an extremely rare case with phenotypes of both LS and MFS. In addition, it is the first known case to show mutations in both responsible genes.