From the Guidelines
Histopathological findings in skin vasculitis variants differ significantly, with leukocytoclastic vasculitis showing fibrinoid necrosis, neutrophilic infiltration, and nuclear dust, while sepsis-induced vasculitis demonstrates microthrombi and endothelial swelling, drug-induced vasculitis presents with eosinophilic infiltrates, and paraneoplastic vasculitis shows a mixed inflammatory infiltrate. The most recent and highest quality study, 1, provides guidance on the diagnosis of small-vessel vasculitis, which is essential for distinguishing between these variants.
Key Histopathological Features
- Leukocytoclastic vasculitis: fibrinoid necrosis of vessel walls, neutrophilic infiltration, nuclear dust (leukocytoclasia), and extravasated erythrocytes primarily affecting small vessels in the superficial dermis
- Sepsis-induced vasculitis: similar neutrophilic infiltration, microthrombi, endothelial swelling, and more extensive vascular damage with possible disseminated intravascular coagulation features
- Drug-induced vasculitis: eosinophilic infiltrates alongside neutrophils, sometimes with granuloma formation, and may affect vessels of various sizes depending on the causative medication
- Paraneoplastic vasculitis: mixed inflammatory infiltrate with lymphocytes and plasma cells in addition to neutrophils, and may have atypical cellular features or more extensive vessel involvement
Importance of Biopsy Timing and Technique
The timing of biopsy is crucial, as early lesions (less than 24-48 hours) show predominant neutrophilic infiltration, while older lesions demonstrate lymphocytic predominance, as noted in 1. When performing punch biopsies, selecting lesions less than 24 hours old provides the most diagnostic yield, and including subcutaneous tissue is important as some vasculitis variants affect deeper vessels, as recommended in 1. These histopathological differences help guide diagnosis and treatment approaches for these clinically similar but pathologically distinct vasculitis variants.
From the Research
Histopathological Findings in Skin Vasculitis
The histopathological findings in skin vasculitis can vary depending on the clinical variant. The following are some key findings:
- Leucocytoclastic vasculitis: characterized by inflammatory infiltrate composed of neutrophils with fibrinoid necrosis and disintegration of nuclei into fragments ("leukocytoclasia") 2, 3, 4, 5
- Sepsis-induced vasculitis: may show similar findings to leucocytoclastic vasculitis, with the addition of features such as bacterial infection and tissue necrosis 6
- Drug-induced vasculitis: may show findings similar to leucocytoclastic vasculitis, with the addition of features such as eosinophilic infiltration and granulomatous reaction 3, 4
- Paraneoplastic vasculitis: may show a range of findings, including leucocytoclastic vasculitis, granulomatous vasculitis, and lymphocytic vasculitis, depending on the underlying malignancy 2, 5
Key Features of Each Variant
Some key features of each variant include:
- Leucocytoclastic vasculitis: palpable purpura, inflammatory infiltrate composed of neutrophils, fibrinoid necrosis, and disintegration of nuclei into fragments ("leukocytoclasia") 2, 3, 4, 5
- Sepsis-induced vasculitis: persistent rash, erythema, liquid drainage, and severe burning pain, with secondary bacterial infection and tissue necrosis 6
- Drug-induced vasculitis: cutaneous small vessel vasculitis, with findings similar to leucocytoclastic vasculitis, and a history of medication use 3, 4
- Paraneoplastic vasculitis: a range of findings, including leucocytoclastic vasculitis, granulomatous vasculitis, and lymphocytic vasculitis, depending on the underlying malignancy, and a history of cancer 2, 5
Diagnostic Considerations
Diagnosis of skin vasculitis requires a comprehensive history, physical examination, and laboratory tests, including: