rs28934568 — TGFBR2

Pathogenic missense variant in TGFBR2 (Leu308Pro) causing Loeys-Dietz syndrome type 2 — a connective tissue disorder with high risk of early aortic aneurysm and dissection requiring lifelong cardiovascular surveillance

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TGFBR2 Leu308Pro — When the Body's Growth Control Goes Wrong

Every blood vessel in your body is held under tension by the interplay of growth signals and structural proteins. One of the most critical regulators of this balance is TGF-β signaling11 TGF-β signaling
the transforming growth factor-beta pathway controls cell proliferation, extracellular matrix production, and tissue repair in nearly every organ system. TGFBR2 encodes the type II receptor for TGF-β — the receptor that first captures the TGF-β signal and kicks off a phosphorylation cascade into the cell nucleus. The Leu308Pro variant (rs28934568, ClinVar VCV000012505) substitutes a leucine with a proline in the kinase domain of this receptor, disrupting the intracellular signaling machinery. The result is Loeys-Dietz syndrome type 222 Loeys-Dietz syndrome type 2
LDS2, OMIM 190182 — one of six LDS subtypes, caused by mutations in TGFBR2 and representing approximately 55-60% of all LDS diagnoses, a multisystem connective tissue disorder in which aortic aneurysm and dissection can occur at unexpectedly small vessel diameters and at younger ages than in comparable conditions like Marfan syndrome.

The Mechanism

TGFBR2 is on chromosome 3 at position 30,672,106 (GRCh38). The T-to-C change at this position converts leucine 308 in the intracellular kinase domain to proline — an amino acid that, due to its cyclic side chain, introduces a rigid kink that disrupts alpha-helical secondary structure. The kinase domain is where TGFBR2 autophosphorylates and phosphorylates its partner receptor TGFBR1, initiating downstream Smad2/Smad3 signaling. Functional studies of related TGFBR2 kinase domain variants confirm that the pathogenic variants reduce Smad2 phosphorylation and TGF-β-induced gene transcription33 the pathogenic variants reduce Smad2 phosphorylation and TGF-β-induced gene transcription
Luo et al. 2020, in vitro assays of a de novo TGFBR2 kinase domain variant, impairing the growth-factor circuit that normally maintains connective tissue homeostasis.

Paradoxically, affected tissues in LDS show increased TGF-β pathway markers — elevated collagen expression, increased phospho-Smad2 in nuclei — even as the mutant receptor impairs direct signaling. This paradox, first described in the original 2005 discovery paper by Loeys and colleagues44 by Loeys and colleagues
Nature Genetics, ten LDS families with TGFBR1/TGFBR2 mutations, is thought to reflect compensatory upregulation of alternative TGF-β signaling routes that overshoots the system, driving excessive extracellular matrix remodeling in the aortic wall. This overactive matrix remodeling weakens the structural integrity of the aorta, predisposing it to aneurysmal dilation and catastrophic dissection.

Inheritance is autosomal dominant — one copy of the pathogenic variant is sufficient for disease. Approximately 75% of LDS cases arise from de novo mutations; 25% are inherited from an affected parent.

The Evidence

A systematic review of 3,896 LDS cases by Gouda et al.55 A systematic review of 3,896 LDS cases by Gouda et al.
International Journal of Cardiology, 2022 established that TGFBR1 and TGFBR2-related LDS (types 1 and 2) carry the most severe aortic phenotype among all LDS subtypes. Aortic dissection occurs at smaller diameters than in Marfan syndrome — a critical clinical distinction. The peripartum aortic dissection rate among 222 pregnant LDS patients was 4%, with 1% peripartum mortality.

GeneReviews management guidelines66 GeneReviews management guidelines
Loeys & Dietz 2008, updated 2024; NCBI Bookshelf NBK1133 specify surgical thresholds of approximately 4.0 cm maximal aortic diameter for TGFBR1/TGFBR2-related LDS — lower than the 5.5 cm threshold used for the general population and the 4.5 cm used for SMAD2/SMAD3-related LDS. This conservative threshold reflects the documented tendency of TGFBR2 variant carriers to dissect at smaller sizes.

Velchev and colleagues77 Velchev and colleagues
2021, Advances in Experimental Medicine and Biology describe the full phenotypic spectrum: arterial tortuosity extends throughout the vascular tree — not just the aortic root — and intracranial, thoracic, and abdominal aneurysms can develop independently. This makes comprehensive arterial imaging essential beyond echocardiography alone.

Practical Actions

Management has four pillars. First, cardiovascular surveillance: annual echocardiography to track aortic root size, with MRA or CT angiography every two years (or annually if growth is detected) to assess the entire arterial tree from head to pelvis. Second, medical therapy: beta-adrenergic blockers or angiotensin receptor blockers (ARBs such as losartan) reduce hemodynamic wall stress and are prescribed from diagnosis in all carriers. Third, activity restriction: contact sports, competitive sports, isometric exercise (heavy weightlifting), decongestants, and triptans (migraine medications) must be avoided. Fourth, family cascade screening: each first-degree relative has a 50% inheritance probability and requires molecular testing or comprehensive cardiovascular evaluation.

Elective surgical repair at aortic diameters approaching 4.0 cm protects against the elevated dissection risk seen at smaller sizes in TGFBR2-related disease. Cardiothoracic surgical planning should begin well before this threshold.

Interactions

TGFBR2 acts in the same TGF-β signaling pathway as TGFBR1 (LDS type 1), SMAD2 (LDS type 4), SMAD3 (LDS type 5), TGFB2 (LDS type 3), and TGFB3 (LDS type 6). While each gene produces a clinically distinct LDS subtype, the downstream pathophysiology — excessive aortic wall remodeling driven by dysregulated TGF-β signaling — is shared. TGFBR2 variants also overlap phenotypically with FBN1 mutations (Marfan syndrome) and COL3A1 mutations (vascular Ehlers-Danlos syndrome), which should be considered in the differential diagnosis during genetic workup when the clinical picture includes significant aortic or arterial disease.

Pregnancy represents a specific interaction: the hemodynamic load of pregnancy combined with the aortic fragility of LDS is a high-risk combination requiring proactive planning with maternal-fetal medicine and cardiology specialists before conception.

Genotype Interpretations

What each possible genotype means for this variant.

TT Non-carrier Normal

No TGFBR2 Leu308Pro variant — standard aortic connective tissue function

You carry two copies of the reference T allele at rs28934568. Your TGFBR2 gene produces a kinase domain with intact signaling capacity, and you do not carry this Loeys-Dietz syndrome pathogenic variant. This is the genotype found in essentially the entire general population — the C (risk) allele is exceptionally rare, detected in only approximately 1 in 50,000 individuals globally.

CC LDS2 Homozygous High Risk

Two copies of Leu308Pro — homozygous TGFBR2 pathogenic variant, extremely rare

You carry two copies of the Leu308Pro pathogenic variant in TGFBR2. Homozygous TGFBR2 pathogenic genotypes are exceptionally rare — essentially absent from population databases — and are not systematically described in the published Loeys-Dietz syndrome literature. If this result is confirmed, it likely represents an exceptionally severe phenotype requiring immediate specialist evaluation at a center with expertise in heritable connective tissue and aortic disorders. One copy of this variant causes LDS2; two copies may result in complete loss of functional TGFBR2 kinase activity.

CT LDS2 Carrier High Risk

One copy of Leu308Pro — pathogenic TGFBR2 variant causing Loeys-Dietz syndrome type 2

TGFBR2 encodes the type II TGF-β receptor, whose intracellular kinase domain initiates downstream Smad2/Smad3 phosphorylation. The Leu308Pro substitution introduces a structurally disruptive proline into an alpha-helical region of this kinase domain, impairing receptor autophosphorylation and the transphosphorylation of TGFBR1 that launches the canonical signaling cascade.

Despite this primary signaling impairment, aortic tissue in LDS paradoxically shows elevated TGF-β pathway markers — including increased nuclear phospho-Smad2 and upregulated connective tissue growth factor. This overshoot, mediated by compensatory non-canonical signaling pathways, drives pathological extracellular matrix remodeling in the aortic media, weakening its structural integrity and predisposing the vessel to progressive dilation and dissection.

Clinical surveillance thresholds for TGFBR2-related LDS are more conservative than for the general population: - Aortic root surgery: recommended when maximal dimension approaches 4.0 cm in adults (lower for children based on body surface area) - Imaging surveillance: annual echocardiography; MRA or CT angiography of the head, chest, abdomen, and pelvis every two years or more frequently if growth is detected - Dissection risk: documented to occur at aortic diameters that would not prompt intervention in the general population or even Marfan syndrome

The full phenotypic spectrum extends beyond the aorta: arterial tortuosity throughout the vascular tree, joint hypermobility, pectus deformities, scoliosis, clubfoot, dystrophic scarring, velvety skin, bifid uvula, cleft palate, hypertelorism, and craniosynostosis. Phenotypic severity varies even within families carrying the same variant (wide intrafamilial variability is documented for LDS).

Penetrance is high but expressivity is variable. Not all carriers will develop aortic aneurysm at the same rate or age — this is why continuous surveillance, not a one-time assessment, is the standard of care.