Defining diabetic dermopathy.

Diabetic dermopathy presents as well-demarcated, hyperpigmented, atrophic depressions, macules or papules located on the anterior surface of the lower legs of diabetic patients. The histopathology remains poorly defined which may in part be due to the fact that the lesions are rarely biopsied. An advantage of studying autopsy material is the ease of obtaining large biopsy specimens. To further define the histopathological features of this entity, we studied tissue taken from characteristic lesions at autopsy. Inclusion criteria included the presence of the lesions and diabetes-related nephroarteriolosclerosis at autopsy. Surprisingly, only four out of 14 skin biopsies showed moderate to severe wall thickening of arterioles or medium-sized arteries on periodic acid Schiff (PAS) stains. Only mild basement membrane thickening was noted in 11 of 14 which was highlighted by the PAS stain. Pigmented material was identified within the dermis of 13 cases. In 10 of the cases, the material was positive for Perl's iron stain. Ten cases had material staining positive for Fontana-Masson in the dermis. Nine cases had markedly increased epidermal melanin. The findings suggest that hemosiderin deposition in conjunction with the deposition of melanin contribute to the clinical features of diabetic dermopathy.