Скачать или смотреть 4. Connective Tissue Biochemistry | Abnormalities in Collagen Biosynthesis | MBBS | USMLE Step 1

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Connective Tissue Biochemistry | Abnormalities in Collagen Biosynthesis | MBBS | USMLE Step 1

Hey future doctors and biochem learners! Collagen is the body’s major structural protein, but when its biosynthesis goes wrong, the result is a spectrum of connective tissue disorders. These abnormalities affect bones, joints, skin, blood vessels, and kidneys, and they are favorite exam questions in MBBS, NEET PG, FMGE, and USMLE Step 1.

In this lecture, we’ll break down the major abnormalities in collagen biosynthesis, their biochemical basis, and their clinical features. 🧬📚

🌟 Key Abnormalities in Collagen Biosynthesis

1️⃣ Scurvy (Vitamin C deficiency) 🍊

Defective hydroxylation of proline & lysine → unstable triple helix.

Clinical 🩺: Bleeding gums, petechiae, poor wound healing, bone pain.

Exam clue: “Child with bleeding gums + corkscrew hairs.”

2️⃣ Osteogenesis Imperfecta (Type I Collagen Defect) 🦴

Mutation in COL1A1/COL1A2 genes.

Clinical 🩺: Brittle bones (multiple fractures), blue sclera, hearing loss, dental imperfections.

Exam clue: “Child with multiple fractures and blue sclera.”

3️⃣ Ehlers–Danlos Syndrome (EDS) 🧵

Defects in collagen synthesis or cross-linking (various enzyme/gene defects).

Clinical 🩺: Hyperextensible skin, hypermobile joints, easy bruising, vascular fragility (Type III collagen defect is most dangerous → arterial rupture).

Exam clue: “Patient with hyperflexible joints and thin stretchy skin.”

4️⃣ Alport Syndrome (Type IV Collagen Defect) 👂👁️

Mutation in COL4A5 gene → defective basement membrane collagen.

Clinical 🩺: Hematuria, progressive renal failure, sensorineural hearing loss, ocular abnormalities.

Exam clue: “Teenager with hematuria + hearing loss + eye changes.”

5️⃣ Menkes Disease (Copper Transport Defect) 🧬

Copper deficiency → impaired activity of lysyl oxidase → defective cross-linking.

Clinical 🩺: Kinky hair, developmental delay, hypothermia, vascular problems.

⚙️ Key Biochemical Steps Affected

Hydroxylation (Vitamin C): Scurvy.

Triple helix mutation (COL1 genes): Osteogenesis imperfecta.

Cross-linking (lysyl oxidase, Cu²⁺): Ehlers–Danlos, Menkes.

Basement membrane collagen (Type IV): Alport syndrome.

🎯 Exam Integration

Scurvy = hydroxylation defect.

OI = Type I collagen mutation.

EDS = cross-linking defect.

Alport = Type IV collagen defect.
👉 These conditions are classic short clinical cases in USMLE Step 1 & NEET PG.

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❓Want us to cover Elastin & Fibrillin Disorders (Marfan syndrome, Emphysema, Cutis laxa) as the next lecture in your Connective Tissue series? Drop your request in the comments below! 😊

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