Small brown spots on the lower shins - Clinical Advisor

Small brown spots on the lower shins

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  • Diabetic Dermopathy_0113 Derm Clinic

A white man, aged 55 years, presented with several discrete, well-demarcated, atrophic, hyperpigmented, nonblanching brown macules on the pretibial aspect of both lower legs. The spots appeared several years ago with no precedent trauma and are asymptomatic.

Neither OTC topical 1% hydroquinone nor 1% hydrocortisone cream had improved the color or number of lesions. The man had been diagnosed with type 2 diabetes at age 35 years. Current medications included metformin (Fortamet, Glucophage, Glumetza, Riomet), exenatide (Byetta), and enalapril (Vasotec).




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Diabetic dermopathy (DD), a significant cutaneous marker of diabetes mellitus (DM), can be diagnosed by close visual inspection and confirmed by biopsy if necessary. DM affects more than 25 million Americans; in 2010, almost 2 million new cases were diagnosed....

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Diabetic dermopathy (DD), a significant cutaneous marker of diabetes mellitus (DM), can be diagnosed by close visual inspection and confirmed by biopsy if necessary. DM affects more than 25 million Americans; in 2010, almost 2 million new cases were diagnosed.

As the leading cause of blindness, kidney failure, and nontraumatic lower-limb amputation, the direct and indirect costs of caring for patients with DM amounted to an estimated $174 billion dollars in 2007, highlighting the need for appropriate screening, early detection, and treatment of complications from this rapidly growing disease.1

Numerous cutaneous conditions are associated with DM. Acanthosis nigricans (AN)—the soft velvety hyperpigmention commonly found around the neck and in the axillae—is highly characteristic and has been closely correlated with insulin resistance for years. In rare instances, AN may instead be a manifestation of a paraneoplastic syndrome; sudden onset of AN after age 50 years should trigger a workup for malignancy, with adenocarcinoma of the stomach being the most common.

Other cutaneous findings associated with DM include diabetic scleredema, necrobiosis lipoidica diabeticorum, Kyrie disease, diabetic bullae, diabetic foot ulcers, periungual erythema, erysipelas-like erythema, rubeosis facei, pigmented purpura, and diabetic dermopathy. Some of these changes are a result of the microangiopathic effects of DM.

Although underappreciated, DD is probably the most common cutaneous manifestation of DM and considered by many to be pathognomonic for DM. The presence of DD is highly significant since it is a reliable marker for potentially serious vascular complications. First described in the 1960s, DD has gone by several names, including shin spots, pigmented pretibial patches, spotted-leg syndrome, and brown spots of DM. The current nomenclature implies its association with the micro- and macrovascular complications of longstanding disease.2

The incidence of DD varies; the largest study of 457 patients found a rate of 13% among patients with DM.3 The longer the duration of DM, the higher the incidence of DD. DD is most common in patients older than age 50 years, with a male-to-female ratio of 2:1.4

Most important, the presence of DD directly correlates with the incidence of both large- and small-vessel complications of DM.2,4 One study showed that 52% of patients with one microvascular complication (retinopathy, nephropathy, or neuropathy) had DD; this rate rose to 81% in patients who had all three microvascular complications.5 Another study demonstrated coronary artery disease in 53% of patients with DD.3 Because of its association with vascular disease, DD may be a surrogate marker for the severity of diabetic complications.

The vascular association initially led researchers to hypothesize an ischemic vascular etiology for DD, but laser Doppler studies have revealed blood flow to be increased within these cutaneous lesions.6 Thus, the current understanding of the pathophysiology is not complete, but existing evidence suggests a combination of impaired or altered wound-healing following minor trauma possibly related to nerve degeneration.

The diagnosis of DD is based primarily on history and clinical findings; in rare instances, a biopsy may be necessary. Histologically, DD shows atrophic rete ridges, thickened superficial blood vessels with hyalinization of arterioles in the papillary dermis, hemosiderin deposition from extravasated erythrocytes, and a mild perivascular lymphocytic infiltrate.7

The characteristic red-brown color is attributable to hemosiderin deposition. Although rarely necessary for a diagnosis of DD, a biopsy may be required to exclude the diagnosis of look-alike or comorbid conditions.

Diabetic dermopathy typically develops as multiple, discrete, well-demarcated, round or oblong, hyperpigmented, brown, nonblanching, atrophic macules asymmetrically distributed primarily on the pretibial aspect of both lower legs (lesions can also be found on the upper extremities, trunk, abdomen, and thighs).8,9

Early lesions may be mistaken for a fungal infection or stasis dermatitis. Although DD shares a similar distribution, stasis dermatitis will classically show hyperpigmentation with scale and lichenification, whereas DD is much more atrophic. Furthermore, DD is asymptomatic whereas stasis dermatitis and fungal infections are usually very pruritic.

Traumatic scars and healed neurotic excoriations may resemble DD morphologically, but the history will help differentiate these conditions as well.

Necrobiosis lipoidica diabeticorum (NLD) is another important diabetes-related cutaneous disease to distinguish from DD. Both conditions are typically asymptomatic and develop bilaterally on the shins, yet there are some distinct clinical, histologic, and biologic differences.

Whereas DD tends to affect middle-aged men, NLD occurs more commonly in younger individuals, with women being affected three times more frequently then men. Although the majority of patients who develop NLD have diabetes, the disease also can occur in individuals without diabetes. DD occurs uniquely in patients with DM.

Unlike DD, NLD is a granulomatous process that typically presents as an isolated, expanding yellow-brown-red waxy lesion with visible telangiectasias and an atrophic epidermal center, although multiple lesions may be present at times. As NLD lesions enlarge they may ulcerate, an uncommon event in DD.

Less common diseases to consider include papulonecrotic tuberculids, pigmented purpuric lichenoid dermatitis of Gougerot-Blum, and Schamberg disease. These diseases can be differentiated clinically or histologically if necessary.

If DD is suspected clinically, the patient should be evaluated for diabetes as well as for the potential for DM-related vascular complications. Consider an ophthalmologic exam to assess for retinopathy; urinalysis, blood urea nitrogen, and creatinine to evaluate for nephropathy; cardiac exam as suggested by a thorough review of systems; and a full neurologic exam to evaluate for neuropathy.

The man in this case was educated about the nature of DD and its associated cardiovascular risks. Appointments with appropriate specialists were made. Unfortunately, there currently is no effective treatment available for the skin lesions.

Lesional color may slowly fade with time, giving the lesions a more scarlike appearance, but stable persistence of lesions is more commonplace. The primary focus should be on controlling diabetes and preventing/managing the microangiopathic complications of the disease. This patient was advised to have close follow-up with his primary-care provider, to whom he should report any new symptoms.

Anthony Trace, PhD, is a fourth-year medical student at Medical College of Virginia Hospitals, Virginia Commonwealth University, in Richmond, where Julia R. Nunley, MD, is professor of dermatology.

References

  1. Centers for Disease Control and Prevention. 2001 National Diabetes Fact Sheet.
  2. Morgan AJ, Schwartz RA. Diabetic dermopathy: A subtle sign with grave implications. J Am Acad Dermatol. 2008;58:447-451.
  3. Romano G, Moretti G, Di Benedetto A, et al. Skin lesions in diabetes mellitus: prevalence and clinical correlations. Diabetes Res Clin Pract. 1998;39:101-106.
  4. Shemer A, Bergman R, Linn S, et al. Diabetic dermopathy and internal complications in diabetes mellitus. Int J Dermatol. 1998;37:113-115.
  5. Houck GM, Morgan MB. A reappraisal of the histologic findings of pigmented pretibial patches of diabetes mellitus. J Cutan Pathol. 2004;31:141-144.
  6. Wigington G, Ngo B, Rendell M. Skin blood flow in diabetic dermopathy. Arch Dermatol. 2004;140:1248-1250. 
  7. McCash S, Emanuel PO. Defining diabetic dermopathy. J Dermatol. 2011;38:988-992.
  8. Sehgal VN, Srivastava G, Aggarwal AK, et al. Noninsulin-dependent, type II diabetes mellitus-related dermatoses: part II. Skinmed. 2011;9:302-308.
  9. Timshina DK, Thappa DM, Agrawal A. A clinical study of dermatoses in diabetes to establish its markers. Indian J Dermatol. 2012;57:20-25. 
  10. All electronic documents accessed December 15, 2012.

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