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FBN1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

FBN1 gene

The FBN1 gene provides instructions for making fibrillin-1, a protein essential for forming the microfibrils that provide structural support and regulate growth factors in the body.

Normal Function

The FBN1 gene provides instructions for making a large protein called fibrillin-1. This protein is transported into the extracellular matrix, where it binds to other proteins to form threadlike filaments called microfibrils. These microfibrils are organized into a network that acts as a scaffold for the assembly of elastic fibers, which enable skin, ligaments, and blood vessels to stretch. This network also supports bones, nerves, muscles, and the lenses of the eyes.

Fibrillin-1 also regulates growth factor proteins, specifically transforming growth factor beta (TGF-β). When stored within the microfibrillar network, TGF-β is inactive. By regulating the release of TGF-β, fibrillin-1 helps control signaling pathways involved in processes such as cell growth, division, and bone formation.

Health Conditions Related to Genetic Changes

Acromicric and Geleophysic dysplasia

Pathogenic variants in the FBN1 gene can cause acromicric dysplasia (characterized by short stature, short limbs, and stiff joints) and geleophysic dysplasia (characterized by abnormalities of the bones, joints, skin, and heart). These variants typically occur in the TGF-β binding-protein-like domain 5 of the protein, disrupting microfibril assembly and causing TGF-β to become abnormally active.

Isolated ectopia lentis

In this condition, the lens of the eye is out of place. Pathogenic variants reduce the amount of functional fibrillin-1 available to form zonular fibers, which normally hold the lens in place. While classified as "isolated," individuals with these variants may later develop features of Marfan syndrome, such as aortic abnormalities.

Marfan syndrome

Over a thousand pathogenic variants in FBN1 can cause Marfan syndrome, a disorder affecting connective tissues. These variants lead to a severe reduction in functional fibrillin-1, affecting tissue elasticity and causing the overactivation of growth factors. This results in the overgrowth and instability of tissues, often manifesting as tall stature, elongated fingers and toes, and heart and eye problems.

Weill-Marchesani syndrome

Pathogenic variants produce an unstable version of fibrillin-1 that interferes with microfibril assembly, weakening connective tissue and leading to eye, heart, and skeletal abnormalities.

Other disorders

  • Stiff skin syndrome: Characterized by hard, thick skin that restricts movement and causes joint deformities.
  • MASS phenotype: Involves abnormalities of the mitral valve, aorta, skeleton, and skin. It overlaps with Marfan syndrome but lacks ectopia lentis, and aortic problems are typically milder.
  • Marfan lipodystrophy syndrome: Characterized by flexible joints, elongated fingers and toes, loss of fatty tissue (lipodystrophy), and a progeroid (premature aging) appearance.

Other Names for This Gene

  • asprosin
  • Marfan syndrome
  • MASS
  • OCTD
  • SGS

Frequently Asked Questions

Most FBN1-related conditions, including Marfan syndrome and isolated ectopia lentis, are inherited in an autosomal dominant pattern. This means only one copy of the altered FBN1 gene is sufficient to cause the disorder. If a parent has the condition, there is a 50% chance that each of their children will inherit the altered gene and develop the condition.
The most critical complications involve the cardiovascular system, particularly the aorta. Individuals should be regularly monitored for aortic root dilation, which can lead to aortic dissection (a tear in the aortic wall) or rupture, both of which are life-threatening emergencies. Regular echocardiograms are essential for early detection and management.
Differentiation relies on a combination of clinical features, imaging studies, and genetic testing. While all are caused by FBN1 variants, the specific location and type of mutation can lead to distinct clinical presentations. For example, acromicric and geleophysic dysplasias involve specific skeletal and facial features, while isolated ectopia lentis primarily affects the eyes, though it may progress to Marfan-like features over time.
Management is typically multidisciplinary and focuses on preventing complications and managing symptoms. This often includes regular monitoring of the cardiovascular system, ophthalmologic care, orthopedic management, and sometimes medication (e.g., beta-blockers or ARBs) to slow aortic dilation. Lifestyle modifications and genetic counseling are also important components of care.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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