Skin, Polyarteritis nodosa

Polyarteritis nodosa is a rare form of vasculitis of medium and small-sized blood vessels. The early stage of the process is characterized by edema of the vessel. This is followed by neutrophils with lymphocytes in and around the vessel wall and eventually progresses to inimal fibrosis of the vessel.

The section shows a punch biopsy of skin with unremarkable epidermis. The underlying deep dermis and subcutis show florid neutrophilic and lymphocytic inflammation in and around medium-sized blood vessels in the form of vasculitis. Often inflammation is so heavy that the vessel wall is nearly obliterated. One vessel shows changes consistent with fibrinoid necrosis.