Palpable purpura indicates inflammation:
When purpura is raised and can be felt, it signals that there is active inflammation of the blood vessel walls (vasculitis). The palpable quality comes from inflammatory cells infiltrating the vessel wall and surrounding tissue, causing edema and a raised, sometimes firm texture. This is called leukocytoclastic vasculitis at the microscopic level. The presence of palpability immediately narrows your differential diagnosis to inflammatory causes and prompts a vasculitis workup.
Pursue inflammatory markers, autoimmune testing, infectious workup, and skin biopsy to identify the vasculitis type.
Common causes of palpable purpura: