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PATIENT STORY

A 30-year-old woman presents with discoloration on both lower legs. She has no personal history of diabetes; however, type 2 diabetes runs in her family. Visible inspection of the lesions is highly suggestive of necrobiosis lipoidica (NL) (Figure 231-1). There is hyperpigmentation, yellow discoloration, atrophy, and telangiectasias. The patient is not overweight and had no symptoms of diabetes. Her blood sugar at this visit is 142 after eating lunch 1 hour prior to testing. The following day, the patient's fasting blood sugar is 121, with a glycosylated hemoglobin of 6.1. The patient is informed of her borderline diabetes, and diet and exercise are prescribed. She is disturbed by her skin appearance and chooses to try a moderate-strength topical corticosteroid for treatment.

FIGURE 231-1

Necrobiosis lipoidica in a 30-year-old woman with impaired glucose tolerance (borderline diabetes). Note the brown pigmentation and prominent blood vessels. (Reproduced with permission from Suraj Reddy, MD.)

INTRODUCTION

  • NL is a chronic granulomatous skin condition with degenerative connective-tissue changes most often seen in patients with diabetes mellitus (DM). It was previously called necrobiosis lipoidica diabeticorum before the recognition of the significant minority of patients with NL who do not have DM.

EPIDEMIOLOGY

  • NL is a rare condition that occurs in approximately 1% (0.3% to 2.3%) of patients with DM.1-4

  • NL primarily affects women (80%), particularly those with type 1 DM, but it can occur with type 2 DM.1,2 Lesions, however, may be more prone to ulceration in men (58% vs. 15% in one study).5 Approximately 75% of patients with NL have or will develop DM.6

  • Average age of onset is 34 years.1,2

  • In a study comparing 212 young patients with type 1 DM, ages 2 to 22 years, with sex- and age-matched control patients, most (68% vs. 26.5% of controls) had at least 1 cutaneous disorder, with 2.3% versus 0% of control patients having NL.4

  • NL has also been reported in patients with Hashimoto thyroiditis.3

  • Cases of familial NL not associated with DM have also been reported.7

ETIOLOGY AND PATHOPHYSIOLOGY

  • The cause of NL remains unknown.

  • Angiopathy leading to thrombosis and occlusion of the cutaneous vessels has been implicated in its etiology. However, microangiopathic changes are less common in lesions on areas other than the shins and, therefore, are not necessary for developing the lesions.2

  • Antibodies and C3 have been found at the dermal–epidermal junction, suggesting vasculitis.

  • The presence of fibrin in these lesions associated with palisading histiocytes may indicate a delayed hypersensitivity reaction.

  • In a microscopy study, Borrelia was detected in 75% of NL lesions overall and 92.7% of inflammatory-rich (38 of 41) versus inflammatory-poor (4 of 15, 26.7%) cases.8 The authors posit ...

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