ESSENTIALS OF DIAGNOSIS
Oval, fawn-colored, scaly eruption following cleavage lines of trunk.
Herald patch precedes eruption by 1–2 weeks.
Pityriasis rosea is a common mild, acute inflammatory disease that is 50% more common in females. Young adults are principally affected, mostly in the spring or fall. Concurrent household cases have been reported.
Itching is common but is usually mild. The diagnosis is made by finding one or more classic lesions. The lesions consist of oval, fawn-colored plaques up to 2 cm in diameter (eFigure 6–20). The centers of the lesions have a crinkled or “cigarette paper” appearance and a collarette scale, ie, a thin bit of scale that is bound at the periphery and free in the center. Only a few lesions in the eruption may have this characteristic appearance, however. Lesions follow cleavage lines on the trunk (so-called Christmas tree pattern, Figure 6–9), and the proximal portions of the extremities are often involved. A variant that affects the flexures (axillae and groin), so-called inverse pityriasis rosea, and a papular variant, especially in black patients, also occur. An initial lesion (“herald patch”) that is often larger than the later lesions often precedes the general eruption by 1–2 weeks. The eruption usually lasts 6–8 weeks and heals without scarring.
Pityriasis rosea. (Used, with permission, from TG Berger, MD, Dept. Dermatology, UCSF.)
Pityriasis rosea with scaling lesions following skin lines and resembling a Christmas tree. (Used, with permission, from EJ Mayeaux, MD in Usatine RP, Smith MA, Mayeaux EJ Jr, Chumley H, Tysinger J. The Color Atlas of Family Medicine. McGraw-Hill, 2009.)
Serologic testing for syphilis should be performed if at least a few perfectly typical lesions are not present and especially if there are palmar and plantar or mucous membrane lesions or adenopathy, features that are suggestive of secondary syphilis (eFigure 6–21) (eFigure 6–22). Tinea corporis may present with red, slightly scaly plaques, but rarely are there more than a few lesions of tinea corporis compared to the many lesions of pityriasis rosea (eFigure 6–23). A potassium hydroxide examination should be performed to exclude a fungal cause. Seborrheic dermatitis on occasion presents on the body with poorly demarcated patches over the sternum, in the pubic area, and in the axillae. Tinea versicolor lacks the typical collarette rimmed lesions (eFigure 6–24). Certain medications (eg, angiotensin-converting enzyme [ACE] inhibitors and metronidazole) and immunizations rarely may induce a skin eruption mimicking pityriasis rosea.
Classic lesions of secondary syphilis include red-brown, copper, or ham-colored macules or papulosquamous lesions on ...