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.
- 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.
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.
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.
• 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 http://commons.wikimedia.org/wiki/File:Characteristically_blue_sclerae_of_patient_with_osteogenesis_imperfecta.jpg under Attribution-Share Alike Creative Commons 3.0
• This work is a derivative of “Ehlers Danlos Syndrome” by Piotr Dołżonek available at http://en.wikipedia.org/wiki/File:Ehlers-Danlos_syndrome4.jpg under Attribution-Share Alike Creative Commons 3.0
• This work is a derivative of “Ehlers Danlos Thumb” by Piotr Dołżonek available at http://en.wikipedia.org/wiki/File:Ehlers-Danlos_thumb.jpg under Attribution-Share Alike Creative Commons 3.0