What is the treatment and cause of pityriasis rosea?

Treatment and Cause of Pityriasis Rosea

Pityriasis rosea is likely caused by human herpesvirus (HHV)-7 and HHV-6 and is best treated with oral acyclovir for severe cases, while most mild cases require only symptomatic management with antihistamines or topical corticosteroids. 1

Cause

Pityriasis rosea is an acute, self-limited papulosquamous dermatosis with the following etiology:

• Human herpesvirus (HHV)-7 and HHV-6 have been implicated as the causative agents in many cases 1
• The condition primarily affects children and young adults between 10-35 years of age, with peak incidence during adolescence 1
• The exact pathophysiological mechanism remains incompletely understood

Clinical Presentation

Initial Presentation

• Herald patch: Present in approximately 80% of patients, this is a larger, more noticeable oval or elliptical lesion that appears first 1
• Prodromal symptoms in about 5% of patients may include:
  • Headache
  • Fever
  • Malaise
  • Fatigue
  • Anorexia
  • Sore throat
  • Enlarged lymph nodes
  • Arthralgia 1

Secondary Eruption

• Generalized bilateral, symmetrical eruption develops 4-14 days after the herald patch
• Lesions continue to erupt in crops over 12-21 days 1
• Typical lesions are:
  • 0.5-1 cm in size
  • Oval or elliptical
  • Dull pink or salmon-colored macules
  • Delicate collarette of scales at the periphery
  • Oriented along Langer lines (skin cleavage lines)
  • "Christmas tree" pattern on the back
  • V-shaped pattern on upper chest 1

Treatment Approach

Mild Cases

• Reassurance and symptomatic treatment are sufficient for most patients 1, 2
• For pruritus:
  • Oral antihistamines (e.g., dexchlorpheniramine) 3
  • Topical corticosteroids for localized itching 4

Moderate to Severe Cases

• Oral acyclovir has shown efficacy in shortening disease duration and improving symptoms 1, 4
• Oral erythromycin may be effective in treating the rash and decreasing itch, though evidence is limited to one small RCT 3, 5
• Ultraviolet phototherapy can be considered for severe or recurrent cases 1, 4

Special Populations

• Pregnant women: Require special attention as pityriasis rosea during pregnancy has been linked to spontaneous abortions 4
• Children: Similar approach to adults, with appropriate dose adjustments

Treatment Efficacy

• The typical course of pityriasis rosea is 6-8 weeks regardless of treatment 1
• Oral erythromycin showed significant improvement in rash compared to placebo (RR 13.00; 95% CI 1.91 to 88.64) and decreased itch scores (difference of 3.95 points, 95% CI 3.37 to 4.53) 3
• Acyclovir may shorten the duration of illness when started early 1, 4

Common Pitfalls and Considerations

1. Misdiagnosis: Pityriasis rosea can be confused with:

   • Secondary syphilis
   • Seborrheic dermatitis
   • Nummular eczema
   • Tinea corporis
   • Viral exanthems
   • Drug eruptions 4

2. Inadequate treatment duration: Allow sufficient time for treatments to work

3. Unnecessary treatment: Remember that most cases resolve spontaneously within 2-12 weeks 3

4. Overlooking atypical presentations: Vesicular variants and other atypical forms can occur and may require different management approaches 5

5. Failure to recognize complications in pregnancy: Monitor pregnant women closely due to potential risk of spontaneous abortion 4

Treatment Algorithm

1. Assess severity:

   • Mild (minimal symptoms): Reassurance and symptomatic treatment
   • Moderate to severe (significant pruritus or extensive lesions): Consider active intervention

2. For symptomatic relief:

   • Oral antihistamines for pruritus
   • Topical corticosteroids for localized itching

3. For moderate to severe cases:

   • Oral acyclovir (most evidence supports this option)
   • Alternative: oral erythromycin

4. For refractory cases:

   • Consider ultraviolet phototherapy
   • Dermatology referral