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#356: (A)dressing the Christmas Tree? Therapies for pityriasis rosea.

What therapies improve resolution of pityriasis rosea (Christmas tree rash)?

Pityriasis rosea is self-limiting. Based on limited evidence, oral corticosteroids reduce itch and rash for ~95% of patients while acyclovir is effective in ~70% of patients versus 30-60% on placebo at 1-2 weeks.  Macrolides likely ineffective.  Little/no evidence for topical corticosteroids or oral antihistamines.

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  • One systematic review1 studying all treatments and 1 acyclovir2 (age 2-60). Outcomes at 2-weeks; statistically significant unless stated.
  • Prednisolone (20mg tapered over 15-days) versus placebo [1 randomized, controlled trial (RCT), 70 patients]:1
    • Resolved itch: 94% versus 32% (placebo).
    • Good/excellent rash improvement: 97% versus 60% (placebo).
  • Acyclovir 400-800mg 5x daily 7-days:1,2
    • Versus placebo/vitamins/no treatment (3 RCTs 141 patients):1
      • Good/excellent rash reduction: 67% versus 28% (control).1
    • Versus no acyclovir with calamine lotion and cetirizine 10mg (both arms) (1 RCT, 24 patients):1
      • Itch resolution: 75% versus 17% (no acyclovir).
      • Lesion score3 (1-5, higher worse, baseline=4.1): 0.9 versus 3 (no acyclovir).
  • Macrolides:
    • Clarithromycin or azithromycin versus placebo (4 RCTs, 207 patients):1
      • Rash/itch improvement: No difference.
    • Erythromycin 1gram daily x7-14 days versus placebo:1
      • Itch score reduction (1-10, more reduction=better) (1 RCT, 34 patients): 5.7 versus 1.8 (placebo).
      • Rash improvement (2 RCTs, 86 patients): No difference.
      • Gastrointestinal upset: 12% versus 6% (placebo).
  • Topical corticosteroids: No RCTs.1
  • Antihistamines:1 Dexchlorpheniramine versus oral betamethasone versus combined (1 RCT, 85 patients).1
    • Dexchlorpheniramine versus Betamethasone: No difference.
    • Either versus combined: No difference in itch, but rash improved more in either alone versus combined (likely spurious).
  • Limitations: Few/small studies, some unblinded.1

  • Distribution of secondary lesions along Langer lines, appearing ≤6 weeks after herald patch. Self-limiting lasting ~45 days with moderate-severe pruritis in 30-50%.1
  • Guidance:4
    • Consider antihistamines or topical/oral corticosteroids if symptoms severe.
    • Consider acyclovir in pregnancy but pityriasis rosea risks inconsistent/unclear. Example, case-series (38 pregnancies) suggesting first-trimester had higher pregnancy loss5 not supported in subsequent case-series (53 and 33 pregnancies).6,7 Treatment effect unknown.
  • Proposed viral etiology (examples HHV-6, HHV-7), with constitutional symptoms ~69%.4
  • Not to be confused with tinea (pityriasis) versicolor, caused by Malassezia yeast genus.8

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  • Jennifer Young MD CCFP-EM
  • Émélie Braschi MD PhD
  • G. Michael Allan MD CCFP

1. Contreras-Ruiz J, Peternel S, Jiménez-Gutiérrez C, et al. Cochrane Database Syst Rev. 2019; 10:CD005068.

2. Rodriguez-Zuniga M, Torres N, Garcia-Perdomo H. An Bras Dermatol. 2018; 93(5):686-95.

3. Das A, Sil A, Das NK, et al. Indian Dermatol Online J. 2015; 6(3):181-4.

4. Villalon-Gomez J. Am Fam Physician. 2018; 97(1):38-44.

5. Drago F, Broccolo F, Zaccaria E, et al. J Am Acad Derma¬tol. 2008; 58(5 suppl 1): S78-S83.

6. Wenger-Oehn L, Graier T, Ambros-Rudolph C, et al. J Dtsch Dermatol Ges. 2022; 20(7):953-959.

7. Stashower J, Bruch K, Mosby A et al. J Am Acad Derm. 2021; 85(6):1648-9.

8. Leung AK, Barankin B, Lam JM, et al. Drugs Context. 2022; 11:2022-9-2.

Authors do not have any conflicts of interest to declare.