Infectious Exanthems

Abstract

An exanthem is a generalized Cutaneous eruption associated with a systemic disease, usually of infectious cause. The actual mechanisms that produce exanthematous skin lesions are not known but certainly involve a number of different processes including direct damage to cells by pathogenic organisms, toxin production by these organisms, and the patient's immune response. Because the skin has a limited repertoire of responses to illness and injury, there is no single skin lesion whose morphology is pathognomonic for a particular infectious disease. Therefore, the exanthem cannot be considered as a separate entity but only as one component of the disease. There is a great tendency in pediatrics to label every exanthem "an erythematous maculopapular rash." Although this term is often correct, by itself it is always incomplete. The distribution, configuration, and evolution of the rash are often critically important. Historical information regarding infectious exposure, general symptoms, and drug use help constitute a brief, initial evaluation. Although the importance of appropriate laboratory studies cannot be denied, they are often not diagnostic during the acute phase of an infectious exanthem. The initial diagnosis is based on history and clinical findings in the great majority of cases. Too often the physician feels pressured to make a diagnosis and initiate treatment immediately in the sick child with fever and rash. If careful initial evaluation of the child fails to yield a diagnosis, sequential observation of the course of illness throughout time is indicated.