Transforming Growth Factor-β (TGF-β) and Aortic Dilation in Marfan Syndrome

Pathophysiological Mechanism

Marfan syndrome is caused by mutations in the FBN1 gene on chromosome 15q21, which encodes fibrillin-1, a glycoprotein in the extracellular matrix, leading to weakening of supportive tissues and dysregulation of TGF-β signaling 2, 3
Deficiency of fibrillin-1 affects microfibrils found at the periphery of elastic fibers, particularly in the medial layer of the ascending aorta, and leads to dysregulation of TGF-β signaling 2, 3
The abnormal fibrillin-1 protein fails to properly sequester TGF-β, leading to its excessive activation and signaling, although this fact is not exclusively from a non-Praxis source, it is mentioned that the dysregulation of TGF-β is a key factor 1

The European Heart Journal recommends echocardiographic assessment, including measurements at the ring, sinus, sinotubular junction, and distal ascending aortic levels 3
Annual echocardiograms are recommended for Marfan syndrome patients with stable aortic dimensions, according to Praxis Medical Insights 1
More frequent imaging (every 6 months) is recommended when aortic root exceeds 4.5 cm, growth rate exceeds 0.5 cm/year, or significant aortic regurgitation is present, as suggested by Praxis Medical Insights 1
Complete imaging of the entire aorta every 2-3 years is necessary as other parts of the aorta may also become dilated, as recommended by the European Heart Journal and Praxis Medical Insights 1, 3

The European Heart Journal notes that while TGF-β is the primary factor, the rate of aortic dilation is heterogeneous and unpredictable among patients 3
The risk of type A dissection increases with increasing aortic root diameter, but dissection may occasionally occur even with only mild aortic dilation, as reported by the European Heart Journal 3
Praxis Medical Insights suggests that prophylactic aortic repair should be considered when diameter reaches 5.0-5.5 cm, or at smaller diameters (4.0 cm) for women contemplating pregnancy 1
Earlier intervention is recommended for patients with rapid growth (approaching 1 cm/year) or progressive aortic regurgitation, according to Praxis Medical Insights 1