1. The patient’s original lesion is dark brown, macular, and ovoid. An additional 15 to 20 oval, papulosquamous lesions are seen elsewhere on her trunk. These are widely scattered, hyperpigmented, and have scaly centers. The long axes of her oval back lesions are parallel with natural lines of cleavage in the skin.
Diagnosis: Pityriasis rosea, which is commonly seen in patients ages 10 to 35 and is about twice as likely to occur in women as in men.
The so-called herald patch appears initially, in a majority of cases, as a salmon-pink patch that can become as large as 5 to 10 cm, on the trunk or arms. The smaller oval lesions begin to appear within a week or two, averaging 1 to 2 cm in diameter; most display the characteristic “centripetal” scaling, clearly sparing the lesions’ periphery and serving as an essentially pathognomic finding.
On darker-skinned patients, the lesions (including the herald patch) will tend to be brown to black. The examiner must then look for the other characteristic aspects of PR, including the oval (as opposed to round) shape, the long axes of which will often parallel the skin tension lines on the back to produce what is termed the “Christmas tree pattern.”
For more information on this case, see “All of Her Friends Say She Has Ringworm.” Clin Rev. 2013;23(2).