BackgroundMarfan syndrome (MFS) is a rare autosomal dominant connective tissue disorder affecting the cardiovascular, skeletal, and ophthalmic systems. This report aimed to describe a novel genetic background and treatment prognosis of MFS.Case presentationA proband was initially diagnosed with bilateral pathologic myopia and suspected MFS. We performed whole exome sequencing and found a pathogenic nonsenseFBN1mutation in the proband, which confirmed the diagnosis of MFS. Notably, we identified a second pathogenic nonsense mutation inSDHB, which increased the risk of tumours. In addition, the proband karyotype was X trisomy, which may cause X trisomy syndrome. At the 6-month follow-up after posterior scleral reinforcement surgery, the proband's visual acuity improved significantly; however, myopia was still progressing.ConclusionsWe report a rare case of MFS with a X trisomy genotype, a mutation inFBN1and a mutation inSDHBfor the first time, and our findings could be helpful for the clinical diagnosis and treatment of this disease.