紅皮症（Erythroderma）

Exfoliative dermatitis (ED) is a definitive term that refers to a scaling erythematous dermatitis involving 90% or more of the cutaneous surface. Exfoliative dermatitis is characterized by erythema and scaling involving the skin's surface and often obscures the primary lesions that are important clues to understanding the evolution of the disease. Clinicians are challenged to find the cause of exfoliative dermatitis by eliciting the h

istory of illness prior to erythema and scaling, by probing with biopsies, and by performing blood studies.

Pathophysiology

An increased skin blood perfusion occurs in exfoliative dermatitis that results in temperature dysregulation (resulting in heat loss and hypothermia) and possible high-output cardiac failure. The basal metabolic rate rises to compensate for the resultant heat loss. Fluid loss by transpiration is increased in proportion to the basal metabolic rate. The situation is similar to that observed in patients following burns (negative nitrogen balance characterized by edema, hypoalbuminemia, loss of muscle mass).

A marked loss of exfoliated scales occurs that may reach 20-30 g/d. This contributes to the hypoalbuminemiacommonly observed in exfoliative dermatitis. Hypoalbuminemia results, in part, from decreased synthesis or increased metabolism of albumin. Edema is a frequent finding, probably resulting from fluid shift into the extracellular spaces. Immune responses may be altered, as evidenced by increased gamma-globulins, increased serum IgE in some cases, and CD4⁺ T-cell lymphocytopenia in the absence of HIV infection.