type III collagen
Summary
Type III collagen is a fibrillar collagen that provides structural support to hollow organs and blood vessels. It is the predominant collagen in early wound healing and is associated with Ehlers-Danlos syndrome type IV when defective.
Detail
Type III collagen is a major fibrillar collagen composed of three α1(III) chains encoded by the COL3A1 gene. It forms thin fibrils (reticular fibers) that provide structural framework for hollow organs including blood vessels, GI tract, uterus, and lymphoid organs. This collagen is highly prevalent in skin, where it comprises about 15-20% of total collagen, and is the first collagen deposited during wound healing before being replaced by the stronger type I collagen. Type III collagen contains more hydroxyproline and hydroxylysine than type I, making it more flexible. Defects in COL3A1 cause Ehlers-Danlos syndrome type IV (vascular type), characterized by arterial rupture, bowel perforation, and uterine rupture due to fragile blood vessels and hollow organs. Unlike other EDS types, joint hypermobility is minimal. The collagen can be identified histologically using silver staining (reticulin stain) and is decreased in normal aging, contributing to skin fragility in elderly patients.
Sources
- Robbins Basic Pathology
- First Aid for the USMLE Step 1
- Lippincott Illustrated Reviews: Biochemistry
- Janeway's Immunobiology
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