Necrobiosis Lipoidica
EPIDEMIOLOGY AND PATHOGENESIS
Coined by Urbach in 1932 as necrobiosis lipoidica diabeticorum, this disorder was named after characteristic histologic findings and was first described in patients with diabetes. Because not all patients have concurrent diabetes, the shortened term, necrobiosis lipoidica (NL), is preferred. Epidemiologic data show that the mean age of onset is around 30 years, with women representing three times more cases than men. The most often quoted statistics concerning the association of NL with diabetes are from a 1966 retrospective study at the Mayo Clinic. Of 171 patients with NL, two-thirds had diabetes at diagnosis, and another 5 percent to 10 percent had glucose tolerance abnormalities. However, in a 1999 study of 65 patients with NL, only 11 percent had diabetes after 15 years of follow-up. Conversely, the prevalence of NL has been found to be only 0.3 percent to 3.0 percent in patients with diabetes. Although lacking full concordance, NL definitely has a strong association with diabetes and remains a valid marker of the disease. The pathogenesis of this skin disease is unclear. Many etiologic mechanisms have been proposed and reviewed. Evidence suggests that the degree of hyperglycemia and diabetic control does not correlate with the presence of NL.
General Foot Care Guidelines for Patients with Diabetes
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· Examine feet every day, including areas between the toes.
· Regular washing of feet with careful drying, especially between the toes.
· Water temperature should always be less than 37°C (98.6°F) and checked first with the hand rather than the foot.
· Barefoot walking in- or outdoors and wearing of shoes without socks is discouraged.
· Daily inspection and palpation of the inside of the shoes for irregular surfaces or foreign objects.
· If vision is impaired, patients should not try to treat their feet (e.g., nails) by themselves.
· Emollients should be used for dry skin but not between the toes.
· Change stockings daily.
· Wearing of stockings with seams inside out or preferably without any seams at all.
· Nails should be cut straight across.
· Corns and calluses should not be cut by patients but by a health care provider.
· The patient must ensure that the feet are examined regularly by a health care provider.
· The patient should seek early health care attention for any blister, cut, scratch, sore, ingrown toenail, or dermatitis.
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CLINICAL FINDINGS: CUTANEOUS LESIONS
Classically, NL presents with one to several sharply demarcated yellow-brown plaques on the anterior pretibial region . The lesions have a violaceous, irregular border that may be raised and indurated. Initially, NL often presents as red-brown papules and nodules that may mimic sarcoid or granuloma annulare (GA). Over time, the lesions flatten, and a central yellow or orange area becomes atrophic, and commonly telangiectasias are visible, taking on the characteristic “glazed-porcelain” sheen. Aside from the shins, other sites of predilection include ankles, calves, thighs, and feet. Fifteen percent of patients develop lesions on the upper extremities and trunk that tend to be more papulonodular. Although pain and pruritus have been reported, most lesions are asymptomatic. Anesthesia of the plaques does occur.
The clinical course is often indolent, with spontaneous remission in less than 20 percent of cases. Over time, the plaques tend to stabilize, and formation of new lesions tapers off. However, the possibility of ulceration, a poor spontaneous remission rate, and cosmetic concerns lead patients to seek treatment. Ulceration, the most serious complication, occurs in approximately 13 percent to 35 percent of cases on the legs. A few cases of squamous cell carcinoma arising in chronic ulcerative lesions of NL have been reported. Multiple reports document the association of NL with GA and sarcoidosis.
TREATMENT
Treatment for NL is disappointing. At this time, only case reports and small, uncontrolled trials provide the basis for treatment decisions. Early application of potent topical glucocorticoids might slow progression. Although some authors report improvement with intralesional injection of glucocorticoids to the active border, the risk of ulceration with this treatment modality should be considered. A few case reports and one series of six patients showed benefit with short-term systemic glucocorticoids. Aspirin and dipyridamole have produced variable results. Anecdotal reports exist that support the use of topical retinoids and topical PUVA. Treatment with fumaric acid esters in 18 patients was reported to improve lesions clinically and histologically.
Given the generally benign nature of the lesions, physicians should consider the adage “do no harm.” Focus should be on prevention of ulcers. When ulceration occurs in patients with NL, the same wound care principles apply as for all diabetic ulcers. Healing of ulcerated lesions with cyclosporine has been demonstrated in several patients. Surgical excision down to fascia and split-thickness skin grafting remain as the last resort for very recalcitrant ulcers in NL.