Practice Essentials
Marfan syndrome (MFS) is an inherited connective tissue disorder noteworthy for its worldwide distribution, relatively high prevalence, and clinical variability. This autosomal dominant syndrome has pleiotropic manifestations involving primarily the ocular, cardiovascular, and skeletal systems. [1, 2] Classic MFS (MFS type 1, MFS1) has been considered a condition caused by the deficiency of a structural extracellular matrix protein, fibrillin-1; however, studies of Marfan mouse models and Marfan-related conditions have expanded our current understanding to a pathogenic model that involves dysregulation of cytokine-transforming growth factor beta (TGFβ) signaling. [3, 4] Patients who have clinical findings of MFS, as well as genetic variants in the transforming growth factor-beta receptor-1 gene (TGFβR1) or the transforming growth factor-beta receptor-2 gene (TGFβR2), are designated as having MFS type 2 (MFS2). [5]
Signs and symptoms of Marfan syndrome
Clinical presentations are as follows:
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Delayed achievement of gross and fine motor milestones due to ligamentous laxity of the hips, knees, ankles, plantar arches, wrists, and fingers
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A decrescendo diastolic murmur from aortic regurgitation
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An ejection click at the apex followed by a holosystolic high-pitched murmur due to mitral prolapse and regurgitation
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Dysrhythmia (a primary feature)
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Abrupt onset of thoracic pain, which occurs in more than 90% of patients with aortic dissection
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Low back
Pathophysiology
Marfan syndrome (MFS) results from heterozygous mutations in the fibrillin-1 gene (FBN1; OMIM #134797), located on chromosome 15 at band q21.1 (15q21.1), which encodes for the glycoprotein fibrillin. Fibrillin is a major building block of microfibrils, which constitute the structural components of the suspensory ligament of the ocular lens and serve as substrates for elastin in the aorta and other connective tissues. Abnormalities involving microfibrils weaken the aortic wall. Progressive aortic dilatation and eventual aortic dissection occur due to the tension caused by left ventricular ejection impulses. Likewise, deficient fibrillin deposition leads to reduced structural integrity of the lens zonules, ligaments, lung airways, and spinal dura.
Production of abnormal fibrillin-1 monomers from the mutated gene disrupts the multimerization of fibrillin-1 and prevents microfibril formation. This pathogenetic mechanism has been termed dominant-negative because the abnormal fibrillin-1 disrupts microfibril formation (although other fibrillin genes still encode normal fibrillin). Evidence of this mechanism is shown in studies of cultured skin fibroblasts from patients with MFS who produce greatly diminished and abnormal microfibrils.
A study by Benarroch et al suggested that clinical variability in MFS may result from alternative splicing of FBN1. [10]
FBN1 mutations cause several Marfan-like disorders, such as the MASS (myopia, mitral valve prolapse, borderline and nonprogressive aortic enlargement, nonspecific skin and skeletal findings) phenotype and isolated ectopia lentis.
Studies have suggested that abnormalities in the transforming growth factor-beta (TGFβ)-signaling pathway may represent a common pathway for the development of the Marfan phenotype. [11] This gene defect ultimately leads to decreased and disordered incorporation of fibrillin into the connective tissue matrix.
The identification of mutations in TGFβR2 in patients with MFS type 2 (MFS2 mapped at 3p24.2-p25) provided direct evidence of abnormal TGFβ signaling in the pathogenesis of MFS.
Abnormalities in TGFβR1 and TGFβR2 were also reported to cause a new dominant syndrome similar to MFS1; it was associated with aortic aneurysm and congenital anomalies, including Loeys-Dietz syndrome (LDS). LDS is an autosomal dominant aortic aneurysm syndrome with widespread systemic involvement (LDS; OMIM #609192). [11] These results define a new group of Marfan syndrome–related connective tissue disorders, namely, TGFβ signalopathies, and include LDS1 and LDS2 (TGFβR1 and TGFβR2) and the SMAD3 and TGFβ2 disorders, with the latter two being classified as Loeys-Dietz-like (or as LDS3 and LDS4).
Shprintzen-Goldberg syndrome (SGS) has been found to be caused by a pathogenic variant in the SKI gene, which encodes a negative regulator of TGFβ signaling. There is phenotypic overlap with MFS and LDS.
A variant of the fibrillin-2 gene, FBN2, causes congenital contractural arachnodactyly, known as Beals syndrome. [12]
Epidemiology
Frequency
United States
MFS is one of the most common single-gene malformation syndromes. MFS1 affects about 1:5000 to 1:10,000 individuals. [13, 7] Estimates suggest that at least 200,000 people in the United States have MFS or a related connective-tissue disorder.
A study by Behr et al found that in patients presenting with a chief complaint of pectus deformity, the incidence of MFS was 5.3%, with the incidence being 20% in persons with combined type pectus deformity. [14]
International
No geographic predilection is known.
Mortality/Morbidity
Cardiovascular disease (aortic dilatation and dissection) is the major cause of morbidity and mortality in MFS. Without proper medical management, MFS can be lethal in young adulthood, with death occurring at an average age of 30-40 years.
Infant morbidity, as related to cardiovascular disease, is due to progression of mitral valve prolapse to mitral regurgitation and often occurs in conjunction with tricuspid prolapse and regurgitation. Progression to congestive heart failure is a leading cause of cardiovascular morbidity and mortality, as well as the leading indicator for cardiovascular surgery.
Death later in life is usually due to chronic aortic regurgitation and ascending aortic dissection. Dissection generally occurs at the aortic root and is uncommon in childhood and adolescence.
A Norwegian study, by Vanem et al, found that out of 84 adults with Marfan syndrome (MFS) first investigated in 2003-2004, 16 (19.0%) were deceased by 2014-2015 follow-up, including 11 (68.8%) who had died of cardiovascular causes. Standardized mortality ratios were 8.20 for men and 3.85 for women. [15]
A study by Reis et al of patients with Marfan syndrome (MFS) found that those who had an aortic root diameter of 45 mm or more at the time of diagnosis had a significantly worse survival rate over the study’s mean 12.4-year follow-up period. [16]
Race
Marfan syndrome is panethnic.
Sex
No sex predilection is known.
Age
MFS may be diagnosed prenatally, at birth, in childhood, during adolescence, or in adulthood. Neonatal presentation is associated with a severe clinical course.
Many clinical features are specific to age. Some features may not present until later in life, a situation that may make early diagnosis in childhood difficult.
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Adult with Marfan syndrome. Note tall and thin build, disproportionately long arms and legs, and kyphoscoliosis.
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Positive wrist (Walker) sign.
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Positive thumb (Steinberg) sign.
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Arachnodactyly.
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Pectus excavatum of moderate severity.
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Hypermobility of finger joints.
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Stretch marks (striae atrophicae) in the lower back.
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Dural ectasia in the lumbosacral region.
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Typical face seen in a girl with Marfan syndrome characterized by dolichocephaly, malar hypoplasia, enophthalmos, retrognathia, and down-slanting palpebral fissures.
