Skin blood flow in necrobiosis lipoidica diabeticorum

Background  Necrobiosis lipoidica diabeticorum (NLD) is a granulomatous skin reaction found in < 1% of diabetic patients. Our purpose was to determine if NLD represented areas of cutaneous ischemia. Methods  Using laser Doppler flowmetry, we measured cutaneous blood flow in nine diabetic patients at NLD lesions and at contiguous uninvolved sites. Flow values were also determined at several reference sites noncontiguous with the NLD lesions and compared to age- and sex-matched controls: 24 diabetic subjects without skin abnormalities, 18 diabetic patients with dermopathy, and 40 nondiabetic subjects. Results  NLD lesions exhibited significantly higher blood flow (4.8 ± 0.7 ml/min/100 g) than areas of unaffected skin close to the lesions (1.2 ± 0.1 ml/min/100 g) (P < 0.01 for both comparisons). There were no significant differences in flow between normal skin sites in NLD patients and normal sites in diabetic patients without skin lesions. Conclusions  Our findings refute the hypothesis that NLD is a manifestation of microvascular ischemic disease of the skin. The increased blood flow seen in NLD lesions suggests an ongoing inflammatory process.