OME Cardiac Modules Practice Test

The key idea is that Marfan syndrome results from a defect in the fibrillin-1 protein, which forms microfibrils that act as a scaffold for elastic fibers in connective tissue. When FBN1 is mutated, these microfibrils are abnormal or deficient, weakening the connective tissue structure. This impaired scaffolding disrupts elastic fiber assembly and integrity, leading to features like aortic root dilation, lens displacement, and tall, long-limbed stature.

Collagen deficiency isn’t the primary issue in Marfan — collagen is a major structural protein in many tissues, but Marfan’s problem lies specifically with the fibrillin microfibrillar framework. Elastin itself isn’t lacking; rather, the defective fibrillin disrupts the organization and function of elastin-containing fibers. Laminin, another basement-membrane component, isn’t implicated in the usual Marfan pathophysiology.

So, the deficiency is in fibrillin-1, the microfibrillar scaffold essential for proper elastic fiber formation.