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

CLINICAL QUESTION

QUESTION CLINIQUE

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

BOTTOM LINE

RÉSULTAT FINAL

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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EVIDENCE

DONNÉES PROBANTES

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:¹Dexchlorpheniramine 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

CONTEXT
CONTEXTE

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