Cutaneous Manifestations of Nutritional Excess: Pathophysiologic Effects of Hyperglycemia and Hyperinsulinemia on the Skin

Necrobiosis Lipoidica

Necrobiosis lipoidica (NL) is a chronic granulomatous skin condition of unknown origin that presents with well-demarcated, yellow-brown, atrophic patches and plaques often found exclusively on the shins. There is a strong association with type 1 diabetes mellitus, with reported rates ranging from 11% to 65% in patients with NL.^58-60 In a recent retrospective study of 236 patients with NL, 58.5% of patients had diabetes.⁶¹ Nevertheless, NL is a rare entity that affects less than 1% of the diabetic population.⁶⁰ Given its correlation with diabetes, it has been postulated that the pathogenesis of NL is due to microvascular ischemic changes resulting from prolonged hyperglycemia.⁶⁰ However, studies revealing an increase in blood flow to NL lesions suggest that the condition may instead be attributed to an inflammatory process.⁶² Despite the disfiguring appearance, the lesions of NL often are asymptomatic. Pain or pruritus may develop secondary to ulceration, which occurs in approximately one-third of patients. Although many treatment options have been attempted—including topical and intralesional corticosteroids, immunomodulators, platelet inhibitors, and phototherapy—efficacy is limited.⁶⁰

Bullosis Diabeticorum

Bullosis diabeticorum (BD) is the abrupt onset of noninflammatory vesicles and bullae developing in the setting of diabetes. The prevalence of BD in the diabetic population ranges from 0.16% to 0.5%.^63-66 Bullosis diabeticorum occasionally has been reported to occur prior to the onset of diabetes, warranting screening hemoglobin A_1c in patients without an established diagnosis of diabetes.⁶⁷ Bullae most commonly present over the acral surfaces, but the lower extremities also are routinely affected. Bullae typically are large and painless, contain clear fluid, and may progress from tense to flaccid over the course of several days. Although histologic analysis reveals nonspecific findings, biopsy may be useful in excluding other bullous disorders. Because BD is a benign condition that spontaneously resolves over several weeks, treatment rarely is pursued.^63,64

Generalized Granuloma Annulare

Generalized granuloma annulare (GA) is an idiopathic inflammatory cutaneous disorder characterized by pink-red, arciform and annular, nonscaly, beaded papules and plaques. Granuloma annulare can be localized or generalized with perforating, patch, and palmoplantar variants. Although the pathogenesis is poorly understood, some studies have demonstrated a correlation between GA and type 1 diabetes mellitus.^68-71 Generalized GA appears to be most strongly associated with diabetes, and approximately 10% to 15% of cases occur in this population.^70,72 Because GA has been reported to precede the diagnosis of diabetes, patients with generalized or recurrent localized GA should be screened for persistent hyperglycemia with a hemoglobin A_1c test.^71,73 Although some GA is self-resolving, treatment options for persevering GA include topical and intralesional steroids, isotretinoin, dapsone, tacrolimus, antimalarials, biologic medications, and psoralen plus UVA therapy.⁷⁴

Final Thoughts

Mechanistic links between common cutaneous conditions and persistent hyperglycemic and hyperinsulinemic states are slowly emerging. Hyperglycemia promotes nonenzymatic glycation of the vascular endothelium as well as formation of AGEs that impair cross-linking of collagen in the skin. The consequent microangiopathic damage may lead to cutaneous conditions such as DD, NL, and BD. In addition to microvascular compromise, impaired collagen cross-linking may result in ichthyosiform skin changes and SD. Hyperinsulinemia causes increased circulating levels of IGF-1, which leads to the overactivation of IGF-1 receptors present on fibroblasts and keratinocytes. This aberrant IGF-1 signaling drives cellular hyperproliferation and differentiation, which may be responsible for cutaneous findings such as AN, KP, and/or acrochordons. An insulin-dependent increase in IGF-1 and androgenic signaling may have implications for hormonally driven inflammatory skin disorders such as acne vulgaris and hidradenitis suppurativa, warranting further investigation.

Physicians should be aware of these dermatologic manifestations and their proposed underlying pathophysiologic mechanisms related to impaired glucose tolerance and insulin resistance. A diagnosis of T2DM is not a prerequisite for metabolic disturbance, and the skin may serve as the first clue to underlying systemic disease. Early identification of these cutaneous conditions may lead to timely patient counseling, lifestyle modification, and/or medical management, preventing the long-term sequelae associated with metabolic disorders.