A 54-year-old man with type 2 diabetes mellitus complained of asymptomatic, slowly enlarging, brownish plaques on the anterior surfaces of both lower legs (see accompanying figure). These lesions developed over the past three years, and various creams had failed to help. These reddish-brown plaques had depressed shiny centers, and dilated deep subcutaneous vessels could be seen through the atrophic skin. Small ulcerations had recently developed on the involved skin.
The answer is D: necrobiosis lipoidica. Necrobiosis lipoidica is an unusual skin disorder that is strongly associated with diabetes mellitus. The female-to-male ratio is 3:1. The condition develops only in a small proportion of patients with diabetes (0.3 percent),1 but its presence is said to be a strong marker for the disease (65 and 42 percent of patients in two series1,2 were diabetic). The condition may precede the diagnosis of diabetes mellitus, but it occurs more commonly in patients with well-established metabolic disease.3 Necrobiosis lipoidica usually develops in the third or fourth decade of life, but it may be seen in younger or older individuals.3
The typical clinical presentation is that of multiple, oval reddish-brown plaques over the anterior portion of the legs (bilateral in 75 percent of cases).3,4 The plaques often slowly enlarge, with the center developing a yellowish sheen and prominent telangiectasias. Ulceration occurs in about one third of diabetic patients with necrobiosis lipoidica,4 and spontaneous remission is relatively uncommon (19 percent). Clinical variants may be solitary and may be seen on the hands, forearms, fingers, face, scalp, and nipples.1 Patients may complain of pruritus, dysesthesia, or pain at the site of lesions. More frequently, however, the lesions of necrobiosis lipoidica are asymptomatic, and it is the cosmetic effect that is of greatest concern to the patient.
The histologic features of necrobiosis lipoidica include poorly defined histiocytic granulomas with necrobiosis in the middle to deep dermis, PAS-positive staining in the areas of necrobiosis, degeneration and thickening of collagen bundles in the dermis, and vascular changes consisting of endothelial swelling, fibrosis, and hyalinization.4
There is no universally satisfactory intervention for necrobiosis lipoidica. Moisturizing of the skin, protection against trauma or skin injury, and measures to improve the circulation of the lower limbs are recommended for all patients with this disease. High-potency topical steroids may be useful in the early, inflammatory phase of necrobiosis lipoidica.4 Likewise, injection of triamcinolone in perilesional skin has been used with success,1 but care should be exercised with local steroid use because ulceration may occur. Surgical intervention may be necessary if these measures are unsuccessful and nonhealing ulcers persist. Plastic surgeons advise excision of the involved area down to fascia and ligation of associated perforating blood vessels followed by split-thickness skin grafts, but lesions often recur within or around the graft.5 The admonition to “do no harm” may be well advised in this disorder.4
Erythema nodosum is an inflammatory process of the deep dermis and subcutaneous fat characterized by shiny, tender, deep, red nodules most commonly on the anterior shins. Resembling bruises, the nodules gradually change from pink to bluish to brown. Fever and arthralgia frequently accompany the rash. Erythema nodosum is most commonly seen following upper respiratory infections, especially those involving Streptococci. Less common causes include other infections, sarcoidosis, inflammatory bowel disease, and drug reactions (especially oral contraceptives).
Pretibial myxedema presents as waxy plaques on the shins, with prominent hair follicles that give the peau d'orange appearance. This condition is most commonly associated with Graves' disease, and it is thought to be caused by thyroid-stimulating hormone-induced deposition of mucin.
Diabetic dermopathy (skin spots) is the most common dermatosis associated with diabetes. Similar to necrobiosis lipoidica, it presents with reddish-brown patches on the shins, but they are usually much smaller (0.5 to 1.0 cm) in size and greater in number (five to 10, or more lesions). Skin spots gradually resolve to leave a brown, atrophic scar. They are thought to be caused by vascular disease, but there is no correlation with the extent or duration of diabetes.
Granuloma annulare may be hard to distinguish from early necrobiosis lipoidica. There are many variants, but granuloma annulare is typically characterized by several papules or nodules that spread to form a ring around normal or slightly depressed skin. Lesions enlarge slowly over a period of months to years and can be yellowish tan, ery-thematous, bluish, or the color of the surrounding skin. They are usually asymptomatic and occur on the distal portion of the legs, feet, hands, or fingers. Spontaneous resolution is common and no treatment is required.