Marfan Syndrome

About this condition

Marfan syndrome is an autosomal dominant connective tissue disorder caused by mutations in FBN1, which encodes fibrillin-1 — a critical structural component of extracellular microfibrils that maintain mechanical integrity and regulate TGF-β signaling. Pathogenic FBN1 variants disrupt microfibril formation, leading to skeletal abnormalities (tall stature, arachnodactyly, pectus deformity, scoliosis), ocular complications (ectopia lentis, myopia, retinal detachment), and the life-threatening cardiovascular manifestations that define the syndrome's natural history.

Marfan syndrome affects approximately 1 in 5,000 to 1 in 10,000 individuals with no ancestral bias. Over 3,800 distinct FBN1 variants have been catalogued. Approximately 90–95% of individuals meeting revised Ghent diagnostic criteria carry a pathogenic FBN1 variant, while 5–10% remain genetically unresolved — likely due to regulatory mutations or deep intronic variants that standard sequencing approaches miss. Approximately 25% of Marfan cases are de novo mutations. Genotype-phenotype correlation is meaningful: haploinsufficiency variants (producing reduced but functional fibrillin-1) typically cause milder aortic disease, while dominant-negative variants (poisoning the microfibril matrix) cause more severe, early-onset aortic progression.

Progressive aortic root dilatation is the primary driver of morbidity and mortality in Marfan syndrome. Prior to modern medical management, sudden aortic dissection was the leading cause of death in the third to fourth decade of life. A confirmed FBN1 pathogenic variant mandates lifelong cardiovascular surveillance via echocardiography to monitor aortic root diameter; prophylactic aortic root surgery is indicated at 5.0 cm (or 4.5 cm with family history of dissection). Beta-blockers and ARBs slow aortic dilatation by reducing dP/dt and blunting TGF-β signaling. Genetic diagnosis enables cascade screening of first-degree relatives — approximately 50% carry the familial variant — identifying presymptomatic carriers who benefit from surveillance before aortic disease progresses to dissection risk.

FBN1 variant type predicts clinical course — haploinsufficiency variants typically cause milder disease, while dominant-negative variants drive aggressive early-onset aortic dilatation requiring intensive surveillance.

Gene locus: FBN1 (15q21.1)

Standard FBN1 panels miss 5–10% of pathogenic variants. These elude detection because they hide in regulatory regions or deep intronic sequences.

The FBN1 variant causing your aortic risk may not be detected

Although FBN1 is the sole gene associated with Marfan syndrome, targeted panels vary in comprehensiveness. Standard exome-focused sequencing captures most of the coding sequence but frequently misses regulatory region variants, deep intronic changes, and complex rearrangements. Approximately 5–10% of clinically affected individuals meeting revised Ghent criteria have negative molecular testing — not because a variant isn't present, but because standard panels aren't designed to find it. Whole genome sequencing provides complete FBN1 coverage including intronic and regulatory regions, capturing the full spectrum of pathogenic variants.

Knowing your FBN1 variant guides your lifelong surveillance strategy

A confirmed FBN1 pathogenic variant does more than confirm diagnosis — it predicts your aortic disease trajectory. Haploinsufficiency variants typically show slower aortic progression and lower dissection risk; dominant-negative variants show aggressive early-onset dilatation. This genotype-phenotype correlation informs surveillance intensity, beta-blocker dosing, and timing of prophylactic surgery. Approximately 50% of first-degree relatives in your family carry the variant. Cascade genetic screening identifies presymptomatic relatives who can begin surveillance before aortic complications emerge.

Tall frame, long fingers, a heart murmur — features that may share a single genetic origin. Confirming the variant defines the surveillance plan that protects your aorta for life.

Marfan Syndrome

Standard FBN1 panels miss 5–10% of pathogenic variants. These elude detection because they hide in regulatory regions or deep intronic sequences.

The FBN1 variant causing your aortic risk may not be detected

Knowing your FBN1 variant guides your lifelong surveillance strategy

One test. A lifetime of answers.

Tall frame, long fingers, a heart murmur — features that may share a single genetic origin. Confirming the variant defines the surveillance plan that protects your aorta for life.

Marfan Syndrome

Standard FBN1 panels miss 5–10% of pathogenic variants. These elude detection because they hide in regulatory regions or deep intronic sequences.

The FBN1 variant causing your aortic risk may not be detected

Knowing your FBN1 variant guides your lifelong surveillance strategy

Others in Rare Diseases

One test. A lifetime of answers.