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 usually mild. The diagnosis is made by finding one or more classic lesions, such as oval, fawn-colored plaques up to 2 cm in diameter (eFigure 6–25). The centers of a few lesions may have a characteristic 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. 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 HS. The Color Atlas and Synopsis of Family Medicine, 3rd ed. McGraw-Hill, 2019.)
Serologic testing for syphilis should be performed unless perfectly typical pityriasis rosea lesions are present. Palmar and plantar or mucous membrane lesions or adenopathy are features suggestive of secondary syphilis (eFigure 6–26) (eFigure 6–27). Tinea corporis may present with a few red, slightly scaly plaques. Rarely, there are more than a few plaques, but the number of plaques do not compare to the number seen in pityriasis rosea (eFigure 6–28). 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 6–29). Guttate or plaque psoriasis is an important diagnostic consideration and biopsy can help differentiate these from pityriasis rosea. 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 the soles of ...