Manifestations of drug reactions urticaria and cutaneous necrotizing venulitis

Abstract

Urticaria is a nonspecific cutaneous reaction pattern characterized clinically by transient pruritic, blanching erythematous wheals. The lesions are usually relatively unimpressive histologically and characterized by dermal edema, vasodilitation, and a sparse infiltrate of mononuclear cells and occasionally eosinophils around dermal venules. In these cases, there is no evidence of vessel wall inflammation or necrosis. These lesions have been referred to as nonvasculitic or simple urticaria. The condition has a clinical course of variable duration, is seldom associated with significant systemic signs or symptoms, and may be due to either hypersensitivity or nonhypersensitivity mechanisms. Drugs are frequently the cause of this type of urticaria and may involve either allergic or pharmacologic mechanisms. In some cases, urticaria-like lesions may show histologic features of inflammation and necrosis of dermal venules (necrotizing venulitis.) This type of clinical-pathologic reaction pattern is characteristic of patients with a syndrome referred to as “urticarial vasculitis” and patients with features of serum sickness or serum-sickness-like syndrome. These illnesses are characterized by a high incidence of associated systemic signs and systems and are thought to be due to immune complex hypersensitivity mechanisms. The syndrome of urticarial vasculitis is rarely due to drugs but may be exacerbated by them. On the other hand serum-sickness-like syndrome is commonly due to drugs. Although cutaneous necrotizing venulitis may be associated with urticarial lesions, it is more often characterized by palpable purpura or other types of skin lesions suggestive of vessel wall necrosis. These cases are thought to be due to immune complex hypersensitivity mechanisms and drugs are a cause.