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May 1984

Dermal Collagen Degradation and PhagocytosisOccurrence in a Horse With Hyperextensible Fragile Skin

Author Affiliations

From the Laboratory of Large Animal Pathology, Kennett Square, Pa (Dr Gunson); the Department of Medicine, College of Veterinary Medicine, University of Florida, Gainesville (Dr Halliwell); and the Department of Pathology, New York State College of Veterinary Medicine, Cornell University, Ithaca (Dr Minor).

Arch Dermatol. 1984;120(5):599-604. doi:10.1001/archderm.1984.01650410041013

• A 2-year-old female horse had large areas of hyperextensible, fragile skin that were interspersed with areas of normal skin. Affected skin tore easily and contained reduced amounts of dermal collagen. Collagen fibers were fragmented and disorganized, and in trichrome-stained sections, many fibers had abnormal red-stained centers. Electron microscopy showed that many collagen fibers had discrete foci of degradation in which the fibrils were fragmented, loosely packed, and widely separated by granular material. Collagen fibril fragments were present in secondary lysosomes in dermal fibroblasts, but there were no degranulated mast cells or inflammatory cells in these areas. This suggested that a noninflammatory degradation and phagocytosis of collagen had occurred in the areas of hyperextensible fragile skin in this horse. Unaffected skin had no signs of collagen degradation or phagocytosis; uniformly cylindrical collagen fibrils were densely packed into morphologically normal fibers.

(Arch Dermatol 1984;120:599-604)