A New Appraisal of Dermatologic Manifestations of Diabetes Mellitus

Dermatoses Demonstrating an Association With Diabetes

Granuloma Annulare

Granuloma annulare (GA) is a dermatologic condition existing in numerous forms. The generalized form has been suggested to have some association with diabetes. The lesions of GA are classically round, flesh-colored to erythematous papules arising in the dermis that may start on the dorsal extremities where the localized form typically presents, though larger annular plaques or patches may exist in the generalized form. Histologically, GA has a characteristic granulomatous infiltrate and palisaded granulomatous dermatitis, depending on the stage of the evolution. Many studies dating back to the mid-20th century have attempted to elucidate a link between GA and diabetes, with numerous reports showing conflicting results across their study populations.^32-36 This issue is further muddled by links between generalized GA and a host of other diseases, such as malignancy, thyroid disease, hepatitis, and human immunodeficiency virus infection. The usual course of GA is spontaneous resolution, including a peculiar phenomenon noted in the literature whereby biopsy of one of the lesions led to clearance of other lesions on the body.³⁷ However, the generalized form may be more difficult to treat, with therapeutic approaches including topical steroids, light therapy, and systemic immunomodulators.

Lichen Planus

A recent small population study in Turkey demonstrated a strong relationship between lichen planus and abnormal glucose tolerance. In this study of 30 patients with lichen planus, approximately half (14/30) had abnormal glucose metabolism and a quarter (8/30) had known diabetes, but larger studies are needed to clarify this relationship.³⁸ Prior to this report, a link between oral lichen planus and diabetes had been shown in larger case series.^39,40 Clinically, one may see white plaques with a characteristic lacy reticular pattern in the mouth. At other cutaneous sites, lichen planus generally appears as pruritic, purple, flat-topped polygonal papules. The clinical finding of lichen planus also is linked with many other disease states, most notably hepatitis C virus, but also thymoma, liver disease, and inflammatory bowel disease, among other associations.⁴¹

Vitiligo

As an autoimmune entity, it stands to reason that vitiligo may be seen more commonly associated with insulin-dependent diabetes, which has been shown to hold true in one study, while no association was found between later-onset NIDDM and vitiligo.⁴² Given the nonspecific nature of this association and the relatively common presentation of vitiligo, no special consideration is likely needed when examining a patient with vitiligo, but its presence should remind the clinician that these autoimmune entities tend to travel together.

Acquired Perforating Dermatosis

Although the classic presentation of acquired perforating dermatosis (Kyrle disease) is linked to renal failure, diabetes also has been connected to its presentation. Extremely rare outside of the setting of chronic renal failure, acquired perforating dermatosis occurs in up to 10% of dialysis patients.^43,44 It is characterized by papules with a central keratin plug, representing transepidermal elimination of keratin, collagen, and other cellular material; its etiology has not been elucidated. The connection between acquired perforating dermatosis and diabetes is not completely clear; it would seem that renal failure is a prerequisite for itspresentation. A large proportion of renal failure necessitating hemodialysis occurs in patients with diabetic nephropathy, which may explain the coincidence of diabetes, renal failure, and acquired perforating dermatosis.⁴⁵ The presentation of this cutaneous finding should not, however, affect treatment of the underlying conditions. Symptom relief in the form of topical steroids can be used as a first-line treatment of these often pruritic lesions.

Eruptive Xanthomas

The link between diabetes and eruptive xanthomas seems to be a rather tenuous one, hinging on the fact that many diabetic patients have abnormalities in carbohydrate and lipid metabolism. A central feature of eruptive xanthomas is an elevation in triglycerides, which can occur in diabetes. Indeed, it has been estimated that only 0.1% of diabetics will develop eruptive xanthomas,⁴⁶ and its main importance may be to prompt the physician to treat the hypertriglyceridemia and consider other concerning possibilities such as acute pancreatitis.

Psoriasis

Psoriasis is a common dermatologic condition that has been shown to have a far-reaching impact both on patients’ quality of life and cardiovascular risk profiles. Data have emerged linking psoriasis with diabetes as an independent risk factor⁴⁷; although this retrospective study had its limitations, it certainly is interesting to note that patients with psoriasis may have an increased risk for developing diabetes. Perhaps more importantly, though, this study also implied that patients with severe psoriasis may present with diabetes that is more difficult to control, evidenced by increased treatment with systemic therapies as opposed to milder forms of intervention such as diet control.⁴⁷ There almost certainly are other confounding factors and further studies would serve to reveal the strength of this association, but it is certainly an intriguing concept. Echoing these findings, a more recent nationwide study from Denmark demonstrated that psoriasis is associated with increased incidence of new-onset diabetes, adjusting for numerous confounding factors.⁴⁸ The relationship between psoriasis and diabetes is worth noting as evidence continues to emerge.