Fig. 1

Basic histopathology of DSLD lesions. a Histology of normal tendon shows bundles and fascicles separated by septa of less organized and somewhat loose connective tissue that contains fibroblasts, loose collagen fibers, adipose tissue and small blood vessels (↓). b A DSLD-affected tendon shows infiltration of proteoglycans (staining dark blue or purple) obscuring the normal architecture of the tendon. c Cellular lesions are visualized as distinct foci consisting of spindly active fibroblasts/tenoblasts, arranged in whorls. The presence of small amounts proteoglycans is limited to the cytoplasm of these cells. d Reveals an area of septum with increased number of fibroblasts containing small amount of proteoglycans (↓). Numerous small blood vessels are present as well (*). All four sections are stained with hematoxylin and eosin