Pityriasis rosea vs Secondary syphilis and tinea corporis
How to tell Pityriasis rosea and Secondary syphilis and tinea corporis apart when a board question makes them look alike.
Pityriasis rosea is herald patch and Christmas tree; secondary syphilis hits palms/soles; tinea corporis is annular KOH-positive ringworm.
Side by side
Pityriasis rosea causes herald patch followed by oval salmon-colored lesions in Christmas-tree distribution on trunk, usually self-limited.
Secondary syphilis causes diffuse rash including palms/soles plus systemic findings; tinea corporis causes annular scaly plaques with central clearing and KOH hyphae.
Likely viral-triggered self-limited papulosquamous eruption follows cleavage lines.
Treponema dissemination causes secondary syphilis; dermatophyte infection invades keratinized stratum corneum.
Herald patch and Christmas-tree trunk distribution support pityriasis rosea.
Palms/soles rash with mucous patches supports syphilis; annular lesion with hyphae supports tinea corporis.
The trap
Annular or papulosquamous rashes overlap, so distribution, palms/soles, and KOH separate them.
The repair move
For papulosquamous rashes on the trunk, check for herald patch, palms/soles, and KOH: (1) PITYRIASIS ROSEA: HERALD PATCH (single large oval scaly plaque) appears 1 to 2 weeks before the diffuse smaller oval plaques in a CHRISTMAS TREE PATTERN on the back along skin lines; sparing palms and soles; usually mild itch; self-limited over 6 to 8 weeks; HHV-6 and HHV-7 implicated; treat with reassurance and topical steroids for itch. (2) SECONDARY SYPHILIS: diffuse maculopapular rash INCLUDING PALMS AND SOLES (and Rocky Mountain spotted fever does the same), often accompanied by condylomata lata (moist gray-white papules in intertriginous areas), mucous patches, generalized lymphadenopathy, malaise; treat with intramuscular benzathine penicillin G; check RPR and confirm with treponemal-specific test (FTA-ABS or TP-PA). (3) TINEA CORPORIS: annular plaque with central clearing and active ADVANCING scaly border (ringworm) on any body part; KOH shows septate hyphae; treat with topical terbinafine or azole.
Try a free question
CoreA 24-year-old woman has 3 weeks of multiple pink, scaly, oval patches on her trunk. The lesions are oriented along skin lines giving a 'Christmas tree' pattern on the back. The eruption was preceded by a single larger 3 cm scaly pink plaque on the chest that appeared 7 days before the rest. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Pityriasis rosea. Pityriasis rosea begins with a herald patch (single larger lesion) followed days to weeks later by smaller pink scaly oval patches in a Christmas tree pattern along Langer lines on the trunk; self-limited within 6-8 weeks; possibly HHV-6/7 associated; treatment is supportive.
Why the other choices are tempting
- B. Secondary syphilis has rash involving the palms and soles with copper-colored macules.
- C. Tinea corporis is annular with central clearing and KOH-positive hyphae.
- D. Guttate psoriasis is small drop-like silvery scaled plaques without herald patch or Christmas tree pattern.
- E. Drug eruption follows specific medication exposure with morbilliform pattern.
Flashcards
Tap a card to flip it.
What initial lesion supports pityriasis rosea?
A herald patch supports pityriasis rosea.
What rash distribution supports secondary syphilis?
Palms and soles involvement supports secondary syphilis.
Quick answers
What is the fastest way to tell Pityriasis rosea from Secondary syphilis and tinea corporis?
Pityriasis rosea is herald patch and Christmas tree; secondary syphilis hits palms/soles; tinea corporis is annular KOH-positive ringworm.
What is the key clue for Pityriasis rosea?
Pityriasis rosea causes herald patch followed by oval salmon-colored lesions in Christmas-tree distribution on trunk, usually self-limited.
What is the key clue for Secondary syphilis and tinea corporis?
Secondary syphilis causes diffuse rash including palms/soles plus systemic findings; tinea corporis causes annular scaly plaques with central clearing and KOH hyphae.
What is the common trap with Pityriasis rosea vs Secondary syphilis and tinea corporis?
Annular or papulosquamous rashes overlap, so distribution, palms/soles, and KOH separate them.