Marfan syndrome (MFS) was the founding member of the "heritable disorders of connective tissue". The cardinal features of this autosomal dominant syndrome are prominently observed in three systems: skeletal, ocular and cardiovascular. It is now well established that defects in the fibrillin gene, the major component of extracellular microfibrils, located on chromosome 15 (FBN1) cause not only classic MFS, but also a large range of milder, overlapping phenotypes.