Dermatopathology of Vasculitis

Overview / DefinitionVasculitis refers to a heterogeneous group of conditions that result in inflammation of blood vessels, leading to vascular damage and subsequent tissue ischemia. In dermatology, vasculitis can manifest with a variety of skin lesions, including purpura, ulcers, and nodules, depending on the size of the affected vessels. EpidemiologyVasculitis can occur at any age, though some forms are more common in specific demographics. For instance: Granulomatosis with polyangiitis: typically affects individuals aged 40-60 years. Microscopic polyangiitis: has a similar age distribution but often presents with renal involvement. Henoch-Schönlein purpura: more common in children, particularly between ages 2-11. Pathophysiology / MechanismThe pathophysiology of vasculitis involves an immune-mediated attack on the vascular walls. The mechanisms vary among types: Immune complex deposition: seen in conditions like Henoch-Schönlein purpura. Anti-neutrophil cytoplasmic antibody (ANCA) positivity: associated with granulomatosis with polyangiitis and microscopic polyangiitis. Direct endothelial injury: can occur in conditions like cutaneous leukocytoclastic vasculitis. Clinical PresentationSkin findings in vasculitis are diverse and can include: Palpable purpura: often located on dependent areas, indicating small-vessel vasculitis. Ulcers: may occur due to necrotizing vasculitis, particularly in larger vessels. Nodules or plaques: seen in conditions like granulomatosis with polyangiitis. Livedo reticularis: indicative of deeper vascular involvement, often associated with systemic disease. Diagnosis / WorkupDiagnosis of vasculitis involves a combination of clinical evaluation and laboratory studies: Histopathology: skin biopsy shows inflammatory infiltrate, often with a predominant neutrophilic component. Serological tests: ANCA titers, complement levels, and specific autoantibody panels. Imaging studies: vascular imaging (e.g., ultrasound, angiography) may be necessary