Collagen Types and Linked Disorders

There are 29 genetically distinct collagens present in animal tissues. Collagen types I, II, III, V and XI self-assemble into D-periodic cross-striated fibrils. Here the D is approximately 67 nm and there is characteristic axial periodicity of collagen. These form the most abundant collagens in vertebrates.

Collagen types I - V

• Type I collagen is found throughout the body except in cartilaginous tissues. It is found in skin, tendon, vascular, ligature, organs and is the main component of bone. It is also synthesized in response to injury and in the fibrous nodules in fibrous diseases. Over 90% of the collagen in the body is type I.
• Type II collagen is the main component of cartilage. It is also found in developing cornea and vitreous humour. These are formed from two or more collagens or co-polymers rather than a single type of collagen.
• Type III collagen is found in the walls of arteries and other hollow organs and usually occurs in the same fibril with type I collagen.
• Type IV forms the bases of cell basement membrane

• Type V collagen and type XI collagen are minor components of tissue and occur as fibrils with type I and type II collagen respectively. Type V forms cell surfaces, hair and placenta.

Collagen linked diseases

Due to the diverse location of the collagen types they are associated with diseases. The collagen linked diseases commonly arise from genetic defects or nutritional deficiencies. These defects often cause problems in the biosynthesis of the collagen molecules, their assembly and posttranslational modification process that makes them their final end form of collagen.

There may be defects in collagen secretion and general production as well. In addition there is excess collagen formation and deposition in scleroderma.

Collagen-related diseases most commonly arise from genetic defects or nutritional deficiencies that affect the biosynthesis, assembly, postranslational modification, secretion, or other processes involved in normal collagen production.

In addition to the above mentioned disorders, excessive deposition of collagen occurs in scleroderma.