Chickenpox is usually diagnosed clinically on the basis of the characteristic rash and successive crops of lesions. Lesions may be found in all stages of development and healing in affected sites. A history of exposure to an infected contact within the incubation period of 10-21 days is also an important clue in the diagnosis.
Childhood chickenpox is usually not heralded by a prodrome; it begins with the onset of an exanthem. In adults and adolescents, chickenpox may be preceded by a prodrome of nausea, myalgia, anorexia, and headache. The triad of rash, malaise, and a low-grade fever can signal disease onset, though the typical patient is infectious for 1-2 days prior to the development of rash.
Small, erythematous macules appear on the scalp, face, trunk, and proximal limbs, with rapid sequential progression over 12-14 hours to papules, clear vesicles, and pustules and subsequent central umbilication and crust formation.
Vesicles may appear on the palms and the soles and on the mucous membranes, together with painful, shallow, oropharyngeal or urogenital ulcers. Intense pruritus commonly accompanies the vesicular stage of the rash.
The typical patient remains infectious for 4-5 days after the rash develops, by which time the last crop of vesicles has usually crusted over.
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