The etiologies of a variety of skin conditions associated with diabetes have not 
been fully explained. One possible etiological factor is diabetic 
microangiopathy, which is known to affect the eyes and kidneys in patients with 
diabetes. There are many mechanisms by which diabetes may cause microangiopathy. 
These include excess sorbitol formation, increased glycation end products, 
oxidative damage, and protein kinase C overactivity. All of these processes 
occur in the skin, and the existence of a cutaneous diabetic microangiopathy has 
been well demonstrated. These microangiopathic changes are associated with 
abnormalities of skin perfusion. Because the skin plays a thermoregulatory role, 
there is significant capillary redundancy in normal skin. In diabetic patients, 
loss of capillaries is associated with a decrease in perfusion reserve. This 
lost reserve is demonstrable under stressed conditions, such as thermal 
stimulation. The associated failure of microvascular perfusion to meet the 
requirements of skin metabolism may result in diverse skin lesions in patients 
with diabetes. Many skin conditions peculiar to diabetes are fairly rare. 
Necrobiosis lipoidica diabeticorum (NLD) and diabetic bullae occur very 
infrequently as compared with diabetic retinopathy and nephropathy. Conversely, 
there is a correlation between diabetic microvascular disease and NLD. This 
correlation also exists with more common skin conditions, such as diabetic 
dermopathy. This relationship suggests that diabetic microangiopathy may 
contribute to these conditions even if it is not primarily causal. Clinically, 
the major significance of diabetic cutaneous microangiopathy is seen in skin 
ulceration which is very common and has a major impact on diabetic patients. 
Many factors contribute to the development of diabetic foot ulcers. Neuropathy, 
decreased large vessel perfusion, increased susceptibility to infection, and 
altered biomechanics all play a role, but there is no doubt that inadequate 
small blood vessel perfusion is a major cause of the inability to heal small 
wounds that eventually results in ulcer formation. The accessibility of skin 
capillaries makes cutaneous diabetic microangiopathy an attractive model for 
research on the evolution of microvascular disease in diabetic patients.