Importance: Necrobiosis lipoidica (NL) is a rare granulomatous condition. Current knowledge of its key features is based on a limited number of studies and case reports, leading to wide variability in the characterization of its defining features, with limited comparison of patients with or without diabetes.
Objective: To evaluate the epidemiologic characteristics, clinical features, and disease associations of NL in patients with or without type 1 or 2 diabetes.
Design, setting, and participants: This multicenter retrospective review included 236 patients aged 15 to 84 years who were evaluated and received a diagnosis of NL at the University of Pennsylvania Health System between January 1, 2008, and July 15, 2018; University of Iowa Hospitals and Clinics between January 1, 2000, and June 15, 2018; and Brigham and Women's Hospital and Massachusetts General Hospital between January 1, 2000, and February 15, 2018.
Main outcomes and measures: Patient demographics, clinical features, medical comorbidities, and biopsy status.
Results: Of the 236 patients with NL, 200 were women and 36 were men, and 182 were white, with a median age at presentation of 50.0 years (interquartile range, 33.0-59.0 years). The diagnosis was biopsy proven in 156 patients (66.1%). Of the 230 patients with location specified, 225 (97.8%) had NL on the lower legs. A total of 138 patients with NL (58.5%; 95% CI, 52.7%-65.3%) had diabetes. The median hemoglobin A1c for patients with diabetes was 8.00% (interquartile range, 6.68%-9.50%) (to convert hemoglobin A1c to proportion of total hemoglobin, multiply by 0.01). Patients with diabetes were significantly younger than patients without diabetes (median age, 45.0 vs 52.0 years; P = .005), and slightly less likely to be female (112 of 138 [81.2%] vs 87 of 96 [90.6%]; P = .046), but lesion characteristics were otherwise comparable. Other notable comorbidities included obesity in 95 of 184 patients (51.6%; 95% CI, 44.4%-58.9%), hypertension in 104 of 230 patients (45.2%), dyslipidemia in 98 of 225 patients (43.6%), and thyroid disease in 56 of 229 patients (24.5%).
Conclusions and relevance: This study of NL supports its associations with diabetes as well as obesity, hypertension, dyslipidemia, and thyroid disease. Younger age and female sex were observed more frequently in patients with diabetes. Otherwise, NL lesions in patients with or without diabetes shared many clinical features, suggesting that risk factors outside of elevated blood glucose may play an important role in the disease. Future studies should evaluate these associations with the goal of further elucidating NL's underlying pathophysiologic characteristics.