A Guide To Skin Conditions Of The Diabetic Foot

By Robert G. Smith, DPM, RPh, CPed

One-third of the 17 million patients with diabetes develop manifestations of the disease that affect their skin.1,2 The cutaneous manifestations and signs of diabetes can heighten the suspicions of the practitioner regarding the diagnosis of these skin conditions. Patients with diabetes who have peripheral sensory neuropathy and impaired circulation are at an increased risk of developing complications from skin and nail conditions like onychomycosis.3 These skin changes of the foot can lead to the formation of a diabetic foot ulcer and potentially limb-threatening infections. There are four categories of skin manifestations in diabetes: skin changes associated with diabetes, cutaneous manifestations of diabetes, cutaneous infections and skin reactions to anti-diabetic treatments. In order to recognize these manifestations and arrive at an appropriate treatment course, one must have a strong grasp of the various ways that diabetes can affect the skin and the lower extremities (see “Understanding How Diabetes Affects The Skin Of The Foot” below). Understanding How Diabetes Affects The Skin Of The Foot Diabetes affects the skin and lower extremities in many ways. Glucose comprises between 35 to 65 percent of the blood in the human epidermis. The transport of glucose into epidermal cells is not dependent on insulin but requires hexokinase and glucose-C-phosphate. The resulting elevated ratio of glucose in the epidermis of diabetic patients does not seem to have a pathological effect with the exception of potentating skin infections with saprophytic organisms like Candida albicans.4 Poor blood glucose control increases the risk for skin and foot manifestations and cutaneous complications with diabetes, and can compromise a patient’s vascular system.5 Researchers have shown that peripheral vascular disease is associated with diabetes.6 Arteriosclerosis of the arteries of the legs results in generalized cutaneous skin changes that may include a waxy appearance, atrophy, a loss of hair growth, skin temperature cooling at the distal digits, nail dystrophy, pallor on elevation and mottling on dependence.7 A reliable sign of large vessel disease is dependent rubor with a delayed return of color greater or equal to 15 seconds after one has applied pressure to the skin.8 Almost all patients with diabetes have capillary basement membrane thickening. However, this does not lead to occlusive microvascular lesions in and of itself.9 Thickening of the vessel walls with perivascular deposition of PAS-positive material and clumping of elastic fibers in the upper dermis are the most prominent histopathologic markers in diabetic skin.4 The signs of microangiopathy may include cutaneous reactive hyperemia and reduced capillary flow. The nail changes associated with microangiopathy include Beau’s lines, pterygium, proximal fold capillary microscopic changes, splinter hemorrhages and yellow nail discoloration.7,10 Pertinent Pointers On Treating Xerosis Generalized xerosis or dry skin is one of the most common skin conditions one will see among patients who have type 2 diabetes. It is particularly prevalent among elderly patients. At times, the foot may become very dry, leading to peeling and cracking. The problem arises with the nerves that control the oil and moisture in the foot. Sebaceous and sweat glands maintain skin lubrication. The glands become atrophied in the presence of autonomic neuropathy. Another reason for dryness is the redistribution of blood flow in the soles by persistent and inappropriate dilatation of arteriovenous shunts. This activity diverts blood away from the skin surface. When this occurs in combination with alterations in the elasticity of the skin (due to non-enzymatic glycosylation of structural proteins and glycoproteins), the skin splits and portals for bacteria are created. Both pruritis and a sensation of burning usually accompany xerosis as principal symptoms. Structural changes occur among the aligned parallel corneocytes in normal skin as a result of xerosis.11 A roughened epidermal surface results from the disruption of these cells. The progression of xerosis follows a defined pattern. Initially, the skin becomes dry and rough with pronounced skin lines. As the condition progresses, superficial scaling with fissuring and erythema develops.

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