**Core Concept:** Marfan syndrome is a genetic disorder affecting connective tissue, primarily caused by mutations in the FBN1 gene (fibrillin-1), which encodes the protein fibulin-1. This results in the abnormal production of fibrillin-1, a protein that contributes to the elasticity of blood vessels, tendons, and the heart. Marfan syndrome is characterized by features of ectodermal dysplasia, skeletal abnormalities, and cardiovascular involvement.

**Why the Correct Answer is Right:** The correct answer is D. Aortic dilation or aneurysm is a key feature of Marfan syndrome, which is caused by the connective tissue abnormality. In Marfan syndrome, the aortic root enlarges due to the thin, fragile, and elongated aortic wall. The dilated aorta can lead to subluxed lenses (lens subluxation is a manifestation of the ocular involvement in Marfan syndrome) and arm span greater than height, which is a consequence of the generalized skeletal abnormalities in the disorder.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because Marfan syndrome primarily affects the cardiovascular system, leading to aortic dilation and subluxed lenses, rather than focusing on the musculoskeletal system.

B. Although Marfan syndrome can manifest with joint hypermobility, this option is incorrect because the primary focus of Marfan syndrome is on cardiovascular and ocular involvement, not musculoskeletal symptoms.

C. This option is incorrect as Marfan syndrome is a systemic disorder affecting various systems, including the cardiovascular system, ocular system, and skeletal system, but not solely affecting the skin and connective tissue.

**Clinical Pearl:** Marfan syndrome is a complex genetic disorder affecting multiple systems, with aortic dilation and subluxed lenses as key features. It is essential to consider this disorder when evaluating patients with aortic dilation, lens abnormalities, and skeletal abnormalities.