DEFINITION OF CUTANEOUS VASCULITIS
The term cutaneous vasculitis is defined broadly as inflammation of the blood vessels of the dermis. Because of its heterogeneity, cutaneous vasculitis has been described by a variety of terms including hypersensitivity vasculitis and cutaneous leukocytoclastic angiitis. However, cutaneous vasculitis is not one specific disease but a manifestation that can be seen in a variety of settings. In >70% of cases, cutaneous vasculitis occurs either as part of a primary systemic vasculitis or as a secondary vasculitis related to an inciting agent or an underlying disease (see “Secondary Vasculitis,” below). In the remaining 30% of cases, cutaneous vasculitis occurs idiopathically.
INCIDENCE AND PREVALENCE OF CUTANEOUS VASCULITIS
Cutaneous vasculitis represents the most commonly encountered vasculitis in clinical practice. The exact incidence of idiopathic cutaneous vasculitis has not been determined due to the predilection for cutaneous vasculitis to be associated with an underlying process and the variability of its clinical course.
PATHOLOGY AND PATHOGENESIS OF CUTANEOUS VASCULITIS
The typical histopathologic feature of cutaneous vasculitis is the presence of vasculitis of small vessels. Postcapillary venules are the most commonly involved vessels; capillaries and arterioles may be involved less frequently. This vasculitis is characterized by a leukocytoclasis, a term that refers to the nuclear debris remaining from the neutrophils that have infiltrated in and around the vessels during the acute stages. In the subacute or chronic stages, mononuclear cells predominate; in certain subgroups, eosinophilic infiltration is seen. Erythrocytes often extravasate from the involved vessels, leading to palpable purpura. Cutaneous arteritis can also occur, which involves slightly larger-sized vessels within the dermis.
CLINICAL AND LABORATORY MANIFESATIONS OF CUTANEOUS VASCULITIS
The hallmark of idiopathic cutaneous vasculitis is the predominance of skin involvement. Skin lesions may appear typically as palpable purpura; however, other cutaneous manifestations of the vasculitis may occur, including macules, papules, vesicles, bullae, subcutaneous nodules, ulcers, and recurrent or chronic urticaria. The skin lesions may be pruritic or even quite painful, with a burning or stinging sensation. Lesions most commonly occur in the lower extremities in ambulatory patients or in the sacral area in bedridden patients due to the effects of hydrostatic forces on the postcapillary venules. Edema may accompany certain lesions, and hyperpigmentation often occurs in areas of recurrent or chronic lesions.
There are no specific laboratory tests diagnostic of idiopathic cutaneous vasculitis. A mild leukocytosis with or without eosinophilia is characteristic, as is an elevated ESR. Laboratory studies should be aimed toward ruling out features to suggest an underlying disease or a systemic vasculitis.
DIAGNOSIS OF CUTANEOUS VASCULITIS
The diagnosis of cutaneous vasculitis is made by the demonstration of vasculitis on biopsy. An important diagnostic principle in patients with cutaneous vasculitis is to search for an etiology of the vasculitis—be it an ...