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INTRODUCTION

The vasculopathies and a somewhat related group, the neutrophilic dermatoses, are relatively infrequently encountered conditions. However, several of these entities have the potential for dramatic and even life-threatening presentation, such as gangrenous cutaneous necrosis, and may be complicated by damage to internal organs. Prompt and accurate diagnosis of these dermatologic emergencies is crucial.

CLINICAL AND HISTOLOGIC DEFINITIONS

Vascular injury is a dynamic process with a limited number of clinical and histologic reaction patterns. Clinical manifestations include edema, mottling in a reticulated pattern (livedo reticularis), and various expressions of subcutaneous hemorrhage or purpura. Hemorrhagic lesions less than 3 mm in diameter are called petechiae, if larger, ecchymoses. Raised or palpable purpura generally indicate the presence of inflammatory cell infiltrates. Severe vascular damage may result in vascular occlusion followed by ischemia, resulting in necrosis, gangrene, and/or ulceration.

Vascular injury may be limited to the skin, but, in many instances, vascular injury is part of a systemic disease. Vascular damage may be the primary disease process, as in polyarteritis nodosa (PAN); a significant component of a complex disease, as in connective tissue disease; or merely a secondary effect of localized injury, such as an arthropod bite or traumatic ulcer.

Histologically, vascular injury may occur with or without inflammation. The composition and cellularity of the associated inflammatory cell infiltrate, as well as the extent of vascular damage, may also vary (Table 9-1).

TABLE 9-1Definitions of Vascular Injury

Vasculitis occurs when inflammatory infiltrates damage blood vessels. Histologic recognition of vasculitis relies on the identification of 2 key components: an inflammatory cell infiltrate and evidence of vascular injury (see Table 9-1; Fig. 9-1). The absence of inflammation, even if vascular damage is present, precludes a diagnosis of vasculitis. The composition and cellularity of the inflammatory infiltrate may correlate with the chronology of the process, but not always. Early on, neutrophils and/or eosinophils may predominate. In the late healing stage, the lesion may be sparsely populated by lymphocytes and macrophages.

FIGURE 9-1

Fibrinoid degeneration. Fibrinoid material is deposited within a vessel. There is also a polymorphonuclear infiltrate.

Unfortunately, the histologic criteria for recognizing vascular injury are somewhat arbitrary, and the minimal essential criteria remain controversial. Various histologic features may be indicative of vascular injury (Table 9-2); however, certain changes, ...

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