FFinalistSouthampton · 2027
Dermatology
AKT · Dermatology/Inflammatory & papulosquamous

Pityriasis rosea

Self-limiting eruption, probably HHV-6/7 reactivation

Overview

An acute, self-limiting papulosquamous eruption (probably HHV-6/7 reactivation) of young adults. A herald patch precedes a fir-tree distribution of oval scaly patches on the trunk. The job is to recognise it, reassure, and exclude secondary syphilis.

Recognise

  • A single 2–5 cm oval scaly "herald patch" days to 2 weeks before the rest
  • Crops of smaller oval pink scaly macules aligned along skin cleavage lines → a "Christmas-tree / fir-tree" pattern on the trunk and proximal limbs
  • A trailing collarette of scale at the lesion edge; mild itch; sometimes a viral prodrome

Red flags

  • Lesions on the palms and soles, or absence of a herald patch → exclude secondary syphilis

Differentials & how to tell them apart

Secondary syphilisinvolves palms and soles, lymphadenopathy, positive serology — the great mimic
Guttate psoriasissmaller raindrop papules, post-streptococcal, no herald patch and no collarette of scale
Tinea corporisannular, KOH positive, fewer lesions
Nummular eczemacoin-shaped eczematous (not oval scaly) plaques

Clinical image

We can't host this one — the image is DermNet's and their licence doesn't cover us republishing it. Their page for it is free to view.

Pityriasis rosea — clinical imagesDermNet

Investigations

Clinical diagnosis. If atypical or palms/soles are involved → syphilis serology. KOH/scrape if tinea is a consideration.

Management

Reassurance — it is self-limiting; treat itch symptomatically only

  1. 1Reassure: self-resolves over 6–12 weeks. Emollient, a mild topical corticosteroid or an antihistamine for itch only.Gate: Involvement of the palms and soles, or no herald patch → check syphilis serology; secondary syphilis is the mimic that must not be missed
  2. 2Severe itch or extensive disease → topical corticosteroid; rarely phototherapy.
Emollients / mild topical corticosteroid / antihistamine — symptomatic itch relief only

Key points

The herald patch plus the Christmas-tree distribution is the recognition pearl. Always keep secondary syphilis in mind. Post-inflammatory pigment change is common in skin of colour.

Monitor & prognosis

Spontaneous resolution; post-inflammatory pigmentation.

Self-limiting over 6–12 weeks with no scarring; recurrence is uncommon.

Source: DermNet (Pityriasis rosea); StatPearls