Types of Collagen and Associated Disorders Note

Types of Collagen and Associated Disorders Collagen occurs in many places throughout the body. Over 90% of the collagen in the body, however, is type I So far, 28 types of collagen have been identified and described. The five most common types are: • • • • • Collagen I: skin, tendon, vascular ligature, organs, bone (main component of the organic part of bone) Collagen II: cartilage (main component of cartilage) Collagen III: reticulate (main component of reticular fibers), commonly found alongside type I. Collagen IV: forms basal lamina, the epithelium-secreted layer of the basement membrane. Collagen V: cell surfaces, hair and placenta 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. Diseases One thousand mutations have been identified in twelve out of more than twenty types of collagen. These mutations can lead to various diseases at the tissue level. Osteogenesis imperfecta – Caused by a mutation in type 1 collagen, dominant autosomal disorder, results in weak bones and irregular connective tissue, some cases can be mild while others can be lethal, mild cases have lowered levels of collagen type 1 while severe cases have structural defects in collagen. Chondrodysplasias – Skeletal disorder believed to be caused by a mutation in type 2 collagen, further research is being conducted to confirm this. Ehlers-Danlos Syndrome – Ten different types of this disorder, which lead to deformities in connective tissue. Some types can be lethal, leading to the rupture of arteries. Each syndrome is caused by a different mutation, for example type four of this disorder is caused by a mutation in collagen type 3. Alport syndrome – Can be passed on genetically, usually as X-linked dominant, but also as both an autosomal dominant and autosomal recessive disorder, sufferers have problems with their kidneys and eyes, loss of hearing can also develop in during the childhood or adolescent years. Osteoporosis – Not inherited genetically, brought on with age, associated with reduced levels of collagen in the skin and bones, growth hormone injections are being researched as a possible treatment to counteract any loss of collagen. Knobloch syndrome – Caused by a mutation in the collagen XVIII gene, patients present with protrusion of the brain tissue and degeneration of the retina, an individual who has family members suffering from the disorder are at an increased risk of developing it themselves as there is a hereditary link.