A 43-year-old man presented with asymptomatic multiple, bilateral, small, brown macules on pretibial areas which had been present for the last 3 years ( Figure 1A ). The patient was diagnosed with type 2 diabetes 18 years ago, with associated retinopathy and nephropathy.
Figure 1 .
(A) Clinical picture. (B) Dermoscopic image shows two central areas (inside blue dotted-line) surrounded by an ill-defined brown peripheral rim. (C) High magnification dermoscopic image. “Ring-like” globular structures can be identified in the brown peripheral rim (black arrows). Fine scarcely branching linear vessels (white arrows) are separated by blurred grayish-white streaks (*) which look like dusky Wickham striae.
Dermoscopic evaluation of the lesions revealed a distinctive pattern which was characterized by a one or multiple central area/s surrounded by an ill-defined brown peripheral rim ( Figure 1B ). “Ring-like” globular structures could be identified in the brown peripheral rim. Finally, central areas dermoscopically demonstrated several fine scarcely branching linear vessels separated by blurred greyish-white streaks which resembled dusky Wickham striae ( Figure 1C ).
The diagnosis of diabetic dermopathy was confirmed by histopathological assessment. These dermoscopic features show an excellent correlation with histologic findings [ 1 , 2 ] . Thus, the greyish-white color of the central area probably corresponds to increased collagen density and fibroblastic proliferation, and the fine branching vessels probably are telangiectasias in the papillary dermis underlying an atrophic epidermis. The brown peripheral rim can be explained by hemosiderin deposition in dermis and increased melanin of basal cells.
Dermoscopic features of diabetic dermopathy (as described above) are different from other diseases that can also present with pretibial pigmented patches, such as early lesions of necrobiosis lipoidica, pigmented purpuric dermatosis or lichen planus.