The generalized rash: part II. Diagnostic approach

Although it is important to begin the evaluation of generalized rash with an inclusive differential diagnosis, the possibilities must be narrowed down by taking a focused history and looking for key clinical features of the rash. Part I of this two-part article lists the common, uncommon, and rare causes of generalized rashes. In part II, the clinical features that help distinguish these rashes are described. These features include key elements of the history (e.g., travel, environmental exposures, personal or family history of atopy); characteristics of individual lesions, such as color, size, shape, and scale; areas of involvement and sparing, with particular attention to palms, soles, face, nails, sun-exposed areas, and extensor and flexor surfaces of extremities; pruritic or painful lesions; systemic symptoms, especially fever; and dermatologic signs, such as blanching, and the Koebner phenomenon.