Vasculitis means inflammation of the blood vessels. The pathological examination thereof is related to the skin venules, and thus, the deposits of fibrin in walls of venules, the accumulation of blood cells in and around such walls, and the presence of nuclear dust of such cells as a result of fractionation, are among the characteristic features of vasculitis in the pathological examination. It is diagnosed by surgical biopsy and pathology. The lesion observed on the skin is palpable purpura. It is seen as a purple-colored, tumorous focus of bleeding. It does not fade when a glass slide is pressed thereon.

In some cases, vasculitis is seen as changes in septa separating lobes in the fatty tissue, such that a nutty-like stiffness called erythema nodosum is formed on the skin. If erythema nodosum is accompanied by symptoms such as hypertension and livedo reticularis, polyarteritis nodosa is deemed. Livedo reticularis is the skin bruising with a net-like appearance.

An another disease accompanied by livedo reticularis and ankle wounds and scars (cicatrix) is livedoid vasculitis.

On the other hand, Henoch-Schönlein vasculitis is a disease with palpable purpura, arthritis, enteritis (bloody diarrhea) and nephritis (bloody urine). It develops following the throat infection, and if not treated appropriately, may result in renal diseases called nephropathy, and ultimately death.

If palpable purpura and asthma are observed together, this condition is named as Churg-Strauss vasculitis.

In some cases, lesions of a patient with hives (urticaria) last more than 24 hours, and leave traces on the skin as they heal, such as eczema, spots and purpura, as well as fever, arthralgia (joint pain), increased leucocyte count, increased sedimentation, and anemia (bloodlessness) are observed in the said patient. This clinical table is called as urticarial vasculitis. It may be originated from an underlying infection, medicines, or cancer. These factors should be investigated.

In systemic lupus erythematosus, purpura associated with thrombocytopenia is seen. There are also some researchers stating that these are vasculitis.

Palpable purpura is not seen in Behçet's disease, but it is believed that the corresponding lesions are vasculitis.