Marfan syndrome is the consequence of mutations throughout FBN1 that decrease the synthesis and quantity of fibrillin 1, while acromicric dysplasia and related disorders are the result of variants of FBN1 restricted to exons 41 and 42 (e.g., Tyr1700Cys, Ser1750Arg) the gene site that encodes the transforming growth factor (TGF)β-binding-protein-like domain 5 of fibrillin 1. The gene discussed is FBN1; the disease is Marfan syndrome.