Marfan Syndrome, Osteogenesis Imperfecta & Ehlers Danlos

Collagen is the key component of connective tissue. Triple helix of individual procollagen chains (composed mainly of Proline and Glycine) are created in the fibroblast. Outside of the fibroblast collagen undergoes extensive posttranslational modification such as crosslinking via Hydroxyl-Lysine. Vitamin C is an essential cofactor for the hydroxylation of lysine and deficiencies (Called scurvy) lead to weak collagen.

Types of Collagen and Collagen Diseases

  • Type I collagen = bones & scar. Abnormal in Osteogenesis Imperfecta
  • Type II Collagen = Cartilage.
  • Type III Collagen = Skin, vessels & granulation tissue.
  • Type IV Collagen = Basement membrane. Abnormal in Alport Syndrome
  • Fibrillin/Elastin = Ligaments & Lungs. Abnormal in Marfan Syndrome & Emphysema

Just think that type 1 is the strongest and it gets progressively weaker with each higher number. Bone (1) supports the whole body, cartilage (2) supports small parts of the body, skin (3) is a relatively weak covering, and basement membrane (4) only supports a layer of individual cells.

Osteogenesis Imperfecta is a genetic disease that causes a defect in type 1 collagen. It results in many fractures, Blue Sclera, and hearing loss.

Blue Sclera of Osteogenesis Imperfecta

Ehlers-Danlos is a disease caused by abnormal collagen synthesis. Different types of Ehlers-Danlos effect different types of collagen. The most common presentation includes “stretchy” skin, easy bruising, aneurysms (due to weak vessels) & hypermobile joints.

Stretchy Skin of Ehlers Danlos

Marfan Syndrome is a disease caused by abnormal Fibrillin (component of elastin) formation. Classically presents as a Tall patient with hypermobile joints. Mitral valve abnormalities and Aortic Dissection are also frequently seen.

Hypermobile Joints of Ehlers Danlos & Marfan Syndrome


Now that you are done with this video you should check out the next video in the Biochemistry section which covers Tay Sachs Disease, Gaucher & Neiman Pick.


Pictures Used:

• This work is a derivative of “Characteristically blue sclerae of patient with osteogenesis imperfecta” by Herbert L. Fred, MD and Hendrik A. van Dijk available at under Attribution-Share Alike Creative Commons 3.0
• This work is a derivative of “Ehlers Danlos Syndrome” by Piotr Dołżonek available at under Attribution-Share Alike Creative Commons 3.0
• This work is a derivative of “Ehlers Danlos Thumb” by Piotr Dołżonek available at under Attribution-Share Alike Creative Commons 3.0

9 thoughts on “Marfan Syndrome, Osteogenesis Imperfecta & Ehlers Danlos”

  1. Hi Brian- I am really loving your videos! My only feedback would be removing/cutting back on explaining how to use the videos on each individual video and make a quick reference to your site to learn how. Thank you so much for sharing these with us!

  2. This webpage is really awesome. Thank you for posting all the high yield information. I realize all this info its really appearing in usmle step 1. Im a foreign medical graduate who failed twice because I didnt prepare as it should I definetely know all this topics are on the test. Now Ive been studying first aid and doing qbanks and nbmes and prepared more efficiently. Im ready to take it in a week. Today I found this site and I’ll just keep watching the videos and explanations just to keep it fresh before the test. Thanks dude!.

    1. It sounds like you are doing all the right things to prepare for the test. I’m sure you will do great. Keep up the good work for just another week and then you will be free! Good luck

  3. Very great and wonderful videos, you are doing avery great helpful effort. ….thank you so much….I wounder if there is any album for radiology images or pathology….I noticed that there are showing up on the exam…I have one failed attempt. iam lost

    1. thanks for the kind words. Unfortunately, I don’t have a good resource for radiology to pass on. Honestly when I am studying that sort of stuff I usually just google it, because I like to see multiple pictures of the same condition and most textbooks only have 1 pic for each topic. Whatever resource you use make sure you focus on chest x rays, CT scans (primarily of the head and thorax) and musculoskeletal imaging. And for all of them focus on findings that obvious. I don’t think they will require you to find suttle things on imaging as they don’t expect you to be a radiologist as a 3rd year medical student. Most of the pictures will have something obvious like a collapsed lung, clearly broken bone or big mass.

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