How is it Diagnosed?
Pityriasis rosea is a self-limiting skin condition characterized by distinctive rashes,
typically seen in adolescents and young adults. The diagnosis is predominantly clinical,
based on the appearance and progression of the rash.
Diagnosis begins with a detailed history, including recent infections, medications, or
systemic symptoms such as malaise or fever. The hallmark of pityriasis rosea is the
appearance of a "herald patch"—a single, round or oval, pinkish lesion with a slightly
raised, scaly border, typically on the trunk. This is followed by the development of
multiple smaller secondary lesions within 1–2 weeks, often aligning along skin cleavage
lines in a "Christmas tree" distribution.
The physical examination focuses on lesion shape, size, distribution, and scale. The rash
is generally non-itchy or mildly itchy. Dermoscopy may be used for clearer visualization
of the fine scaling at the edges.
Pityriasis rosea can sometimes mimic other conditions such as tinea corporis,
secondary syphilis, psoriasis, or drug eruptions. Therefore, differential diagnosis is
essential. When in doubt, a KOH test may be done to rule out fungal infections, while
serologic testing for syphilis (e.g., VDRL) is considered if lesions are atypical or in
sexually active individuals. A skin biopsy may rarely be needed for confirmation in
atypical presentations.
No specific laboratory tests are required in most cases. Diagnosis helps in reassuring
patients as the condition usually resolves spontaneously within 6–8 weeks without
treatment, although symptomatic relief may be offered with antihistamines or topical
corticosteroids.