Cartilaginous metaplasia in calcified diabetic peripheral vascular disease: morphologic evidence of enchondral ossification.

The mechanism of arterial calcification is not clear. We examined histological sections of major arteries from lower extremities of two patients with longstanding type II (or non-insulin-dependent) diabetes mellitus, and found morphological evidence of cartilaginous metaplasia and ectopic ossification with associated severe medial arterial calcification and atherosclerosis. Hematoxylin and eosin, alcian blue, and toluidine blue stains were applied for the demonstration of cartilage cells and their specific matrix proteins, and immunohistochemical studies for type II collagen. To our knowledge, cartilaginous metaplasia has not previously been described in medium-sized human muscular arteries. This observation supports the hypothesis that active enchondral ossification may be a pathway leading to arterial calcification in diabetic obstructive peripheral vascular disease.