Necrobiosis lipoidica
Definition & Pathogenesis
- Necrobiosis lipoidica (NL, formerly Necrobiosis lipoidica diabeticorum) = idiopathic / diabetes-associated granulomatous dermatosis with collagen degeneration + lipid deposition.
- Pathogenesis: Suspected mechanisms are microangiopathy + immune complex vasculitis + disturbed collagen metabolism + increased TGF-β / adhesion molecule expression + Th1-driven granuloma formation.
- Diabetes association: Correct regarding the association NL ↔ diabetes is approx. 11–65 % of NL patients have diabetes (type 1 > type 2), but only < 0.3–1 % of diabetics develop NL — diabetes control does NOT correlate with course of skin lesions.
- Associated diseases: thyroid autoimmunity, inflammatory bowel diseases, rheumatoid arthritis, sarcoidosis comorbidity discussed.
Clinical Presentation
- Location: Predilection is pretibial bilateral (> 85 %), less often thigh, forearm, hands, scalp.
- Morphology: Classic efflorescence is sharply demarcated, yellowish-orange atrophic plaques with livid-erythematous border + visible telangiectasias ("waxy" atrophy).
- Ulceration: Ulceration risk is approx. 25–35 % in course, often painful, poorly healing, banal-trauma-associated.
- Symptoms: long asymptomatic, later pain / hypoesthesia (nerve fiber destruction in plaque), pruritus possible.
- Course: chronic progressive, spontaneous remission rare (< 20 %).
Diagnostics
- Clinical usually diagnostic (typical yellowish-atrophic pretibial plaques).
- Histology: Pathognomonic are palisading granulomas around necrobiosis zones (degenerated collagen bundles) throughout the entire dermis, "horizontally layered/tiered", plasma cell involvement, possibly lipid deposits.
- Laboratory: fasting blood glucose / oGTT / HbA1c (diabetes screening), thyroid parameters, possibly ANA / RF / ACE.
- In ulceration: biopsy of border → SCC exclusion (rarely squamous cell carcinoma on chronic NL).
Differential diagnoses
- Granuloma annulare
- Diabetic dermopathy
- Morphea
- Limited systemic sclerosis (CREST syndrome)
- Cutaneous sarcoidosis
- Erythema ab igne
- Venous leg ulcer
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Note: This page is intended for medical education and does not replace diagnosis or treatment decisions in individual cases. Treatment and follow-up content is available in the app.