In the absence of a family history, Marfan syndrome can be diagnosed by:   1. Aortic dilation (Z score ≥ 2 SD+) AND ectopia lentis*   2. Aortic dilation (Z score ≥ 2 SD) AND FBN1 mutation   3. Aortic dilation (Z score ≥ 2 SD) AND Systemic Score ≥ 7 points*   4. Ectopia lentis AND FBN1 mutation associated with known aortic dilation In the presence of a family history of MFS, MFS can be diagnosed by the presence of:   5. Ectopia lentis   6. Systemic Score ≥ 7 points*   7. Aortic dilation (Z score ≥ 2 SD when above 20 years of age, ≥ 3 SD when below 20 years of age)* + the Z score is the population score adjusted for surface body area *Caveat: without discriminating features of Shprintzen Goldberg, Loeys-Dietz, or vascular Ehlers-Danlos syndrome Other related conditions: Ectopia lentis syndrome: isolated ectopia lentis with no FBN1 mutation or FBN1 mutation not thought to be associated with aortic dilation MASS phenotype: mitral valve prolapse, stable mild aortic dilation (upper limit of normal), skin striae, with at least one skeletal feature without ectopia lentis Marfan-like body habitus: Systemic Score ≥ 7 without any other features of MFS