[Cutaneous vasculitis and vasculopathy : Differential diagnosis in biopsies of the lower extremities]

The skin is one of the most frequently involved organs in primary systemic and secondary vasculitis; moreover, a vasculitis can occur as single organ vasculitis, limited to the skin. For most types of vasculitis, the lower extremities constitute common sites with clinical symptoms of palpable purpura, nodules, and ulcers. In histopathology of cutaneous vasculitis, it is of utmost importance to correctly identify the vessel types involved and to discriminate between vasculitic vessel damage, unspecific reactive vessel changes, vascular occlusive diseases, noninflammatory purpura, or perivascular infiltrates due to other inflammatory skin diseases. Small-vessel vasculitis is the most frequent type of cutaneous vasculitis; during florid phases, a dermal leukocytoclastic vasculitis is found regardless of etiology. Additional extravascular changes may give etiological clues, however, a correlation with the clinical picture, radiology, and serology is essential. The biopsy type and technique need to be adjusted to the suspected diagnosis and site of the vessels involved. Polyarteritis nodosa and nodular vasculitis can be diagnosed only in biopsies with sufficient subcutaneous tissue. Especially in cutaneous ulcers, a lateral rim of vital skin and subcutaneous tissue is indispensable for a correct diagnosis. Large-vessel vasculitis is not found in skin biopsies of the lower extremities.