Expansion
Type I bone and skin, II cartilage, III reticular, IV basement membrane
Expansion
| Type | Location | Disease when defective |
|---|---|---|
| I | Bone, skin, tendon, dentine; 90 per cent of body collagen | Osteogenesis imperfecta, Ehlers-Danlos |
| II | Cartilage, vitreous, nucleus pulposus | Chondrodysplasias |
| III | Reticular fibres: granulation tissue, liver, spleen, marrow, blood vessels | Vascular Ehlers-Danlos |
| IV | Basement membrane | Alport syndrome, Goodpasture disease |
| V | Placenta, associated with type I | Classical Ehlers-Danlos |
| VII | Anchoring fibrils | Dystrophic epidermolysis bullosa |
The mnemonic Be So Totally Cool, Read Books maps the first four: Bone and Skin for I, Cartilage for II, Reticular for III, Basement membrane for IV.
Wound healing switches type: type III predominates in early granulation tissue and is progressively replaced by type I during remodelling, which is why tensile strength continues to increase for months.
Osteogenesis imperfecta typically results from a glycine substitution in type I collagen, which is disproportionately damaging because glycine must occupy every third position in the triple helix.