Anatomy of striae.

The histopathology of striae distensae is disputed; different authorities give contradictory accounts of the microscopic changes, especially in elastic fibres. We re-evaluated the problem by taking eight elliptical biopsies across striae. Six were examined by light microscopy with appropriate stains for elastin and collagen. Two were prepared for scanning electronmicroscopy (s.e.m.), using a procedure which removes collagen, enabling the elastic network to be seen in its native form. By light microscopy, striae were sharply demarcated from normal skin, consisting mainly of fine, straight bundles of collagen arranged parallel to the surface. Fine elastic fibres were disposed similarly without fragmentation, fraying or curling. By s.e.m., the elastic network was found to be extraordinarily dense and well developed with many fine, curled fibres in random array. It was evident that the routine stains for elastin greatly underestimated the abundance of elastic fibres, probably because immature fibres contain insufficient protein matrix. The horizontal packing of collagen bundles was confirmed by s.e.m. These findings support the view that striae distensae are scars. There is no evidence that they form by stress-induced rupture of the connective tissue.