Скачать или смотреть 6. Connective Tissue Biochemistry | Fibrillin Structure & Clinical Aspects (Marfan Syndrome) USMLE

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Connective Tissue Biochemistry | Fibrillin Structure & Clinical Aspects (Marfan Syndrome) | MBBS | USMLE Step 1

👋 Hey future doctors and biochem learners! Along with collagen and elastin, fibrillin is a critical protein of connective tissue. It acts as the scaffold for elastin deposition, ensuring the strength and elasticity of tissues like aorta, ligaments, and the eye lens.

In this lecture, we’ll discuss the structure and function of fibrillin, its role in connective tissue integrity, and the applied clinical aspects — especially Marfan syndrome, one of the most high-yield genetic disorders tested in exams. 🧬📚

🌟 Structure & Function of Fibrillin

Large glycoprotein found in the extracellular matrix.

Secreted by fibroblasts → polymerizes into microfibrils.

Microfibrils form the framework on which elastin is deposited, helping build elastic fibers.

Provides tensile strength and regulates growth factor signaling (TGF-β sequestration).

🩺 Applied Clinical Aspects

1️⃣ Marfan Syndrome 🧬

Defect: Mutation in FBN1 gene (chromosome 15) → abnormal fibrillin-1.

Pathophysiology: Defective microfibrils → impaired elastin deposition + abnormal TGF-β signaling → weakened connective tissue.

Clinical features:
• Tall stature with long limbs (arachnodactyly).
• Hyperextensible joints.
• Lens dislocation (subluxation, typically upward & outward).
• Aortic aneurysm & dissection (life-threatening).

Exam clue: “Tall patient with lens subluxation and aortic root dilation.”

2️⃣ Other Associations

Weakened connective tissue in ligaments → scoliosis, pectus excavatum/carinatum.

Cardiovascular risk is the most important determinant of prognosis.

⚙️ Clinical Management (Basics)

Beta-blockers (reduce aortic wall stress).

Losartan (blocks TGF-β signaling).

Surgical repair for aortic aneurysm if needed.

🎯 Exam Integration

Fibrillin forms microfibrils = scaffold for elastin.

FBN1 mutation = Marfan syndrome.

Key triad: Tall stature + lens subluxation + aortic aneurysm.
👉 A favorite exam topic in USMLE Step 1 & NEET PG case-based questions.

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❓Want us to make a comparative lecture: Collagen vs Elastin vs Fibrillin (structure, synthesis, disorders) for your Connective Tissue playlist? Drop your request in the comments below! 😊

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