An unusual dermal collagen disorder in a dog

An adult dog developed a connective tissue disorder characterized by hyperextensibility of the skin on the head, neck and shoulders. Under light microscopy, the thickness of the dermis was reduced and the collagen bundles were fragmented. Hypodermic lesions appeared as fat necrosis and swelling of the wall of the blood vessels. Electron microscopically, the packing of collagen bundles and fibres in the dermis was highly disorganized and the rough endoplasmic reticulum of fibroblasts showed dilatation of the cisternae. Whereas the dermal lesions were non-specific, this case differed fundamentally from canine inherited collagen diseases in that the clinical features appeared in an old dog and the dermal lesions were only localized and were associated with hypodermal atrophy.