Pityriasis Rosea

Snapshot

• A 10-year-old boy is brought to his dermatologist for a developing rash. A couple of weeks ago, he recovered from a common cold. A week after, he developed an oval rash on his chest. Thinking it was a fungus infection, his parents applied anti-fungal cream to the area. However, a week after the first lesion appeared, he developed multiple smaller rashes in his lower abdomen. They are sometimes itchy, but only mildly so.

Introduction

• Common, self-limited papulosquamous eruption
• Pathogenesis
  • idiopathic
  • often associated with URI
  • seasonal pattern suggests viral etiology, though not confirmed
    • potential link to herpesvirus types 6 and 7
• Epidemiology
  • children
• young adults

Presentation

• Symptoms
  • prodrome or URI within a month of onset
  • little or no pruritus
• Physical exam 
  • herald patch, a single lesion
    • usually on the trunk
    • plaque with thin collarette of scale inside the border
  • eruption in 1-2 weeks
    • multiple smaller papules appear in “Christmas tree” distribution
      • oriented along Langer (skin cleavage) lines
    • rose-colored or violet
  • resolution in 4-12 weeks
• resolves spontaneously without scarring

Evaluation

• Diagnosis from clinical exam and history
• Diagnosis confirmed with skin biopsy
• potassium hydroxide preparation to exclude Tinea spp.

Differential Diagnosis

• Tinea corporis 
• Secondary syphilis (especially if palm and soles involved) 
• Tinea versicolor 
• Drug eruption 
• Guttate psoriasis

Treatment

• Observation
  • lesions heal within 4-12 weeks
• Natural sunlight

Prognosis, Prevention, and Complications

• Prognosis
  • very good
  • typically self-limited and self-resolving in 4-12 weeks
• Complications
  • relapse