Pityriasis Rosea

Pityriasis rosea is an acute, self-limited skin disease. The etiology is not known, and it commonly occurs in young adults. Patients initially present with a single, ovoid “herald patch.” This is followed by diffuse, pruritic, scaly, oval lesions over the trunk (often in a “Christmas tree” distribution on the back) and extremities. The diagnosis is clinical. Pityriasis rosea is a self-limiting condition; therefore, usually no treatment is required. However, topical steroids and antihistamines may be used for pruritus, if needed.

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Epidemiology and Etiology

Epidemiology

  • Incidence: 0.5%–2%
  • Sex: women > men
  • Common age group: 15–30 years
  • Seasonal variation: more common in winter and spring (in temperate climates)

Etiology

  • Idiopathic
  • Possibly infectious; has been associated with:
    • HHV-6
    • HHV-7
    • HHV-8
    • Influenza (H1N1)

Clinical Presentation

Prodrome

  • Occurs in a minority of patients a week prior to appearance of cutaneous lesions
  • Symptoms:
    • Malaise 
    • Headache
    • Fever  
    • Arthralgia
    • Sore throat

Cutaneous eruption

Primary:

  • Called the “herald” or  “mother” patch
  • Single lesion
  • Round or oval 
  • 2–5 cm in diameter
  • Well-defined borders
  • Pink or salmon-colored 
  • Collarette scaling:
    • Fine scaling that remains attached near the border
    • Scale lifts up near the center of the lesion.
    • Center may appear wrinkled.
  • Located on: 
    • Back
    • Chest 
    • Neck

Secondary:

  • Occurs within 1–2 weeks after the herald patch 
  • Same features as the herald patch, except:
    • Smaller (< 1.5 cm)
    • Appears in crops
    • Symmetrical
    • Bilateral 
  • Located on: 
    • Back
    • Chest
    • Extremities
  • “Christmas tree” distribution 
    • Term used to describe the rash’s appearance on the back
    • Due to the lesions’ orientation along skin tension lines (Langer’s lines)
  • Pruritus usually present (severe in 25% of cases)
  • Usually resolves spontaneously in 6–8 weeks: 
    • Generally leaves few residual cutaneous changes
    • Postinflammatory hyperpigmentation is common in dark-skinned patients.

Diagnosis and Management

Diagnosis

Pityriasis rosea is a clinical diagnosis. The following tests may be used if the diagnosis is not clear.

  • Skin biopsy:
    • Rarely needed
    • Findings:
      • Superficial perivascular infiltrate (lymphocytes and histiocytes)
      • Focal parakeratosis
  • KOH examination of scales → rule out tinea corporis 
  • Rapid plasma reagin and VDRL tests → rule out secondary syphilis

Management

Pityriasis rosea is a self-limiting condition; therefore, usually no treatment is required. 

  • General:
    • Reassurance
    • Emollients
  • Medical management:
    • Pruritus: 
      • Topical corticosteroids 
      • Oral antihistamines
      • Menthol
    • Severe symptoms: 
      • Acyclovir 
      • Ultraviolet light therapy

Complications

  • In pregnant patients (especially if occurring within the first 15 weeks):
    • Miscarriage and spontaneous abortion
    • Premature delivery
    • Neonatal hypotonia 
  • Bacterial superinfections are rare.

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Differential Diagnosis

  • Tinea corporis: a superficial fungal infection of the skin that can affect the face, trunk, and extremities: The lesions of tinea corporis are characterized by peripheral scaling, central clearing, and erythema. The appearance may be similar to that of the herald patch of pityriasis rosea. The diagnosis is usually clinical, though a KOH examination would show fungal hyphae. Management includes topical or oral antifungal medications. 
  • Tinea versicolor: a fungal skin infection due to Malassezia furfur: Multiple scaly patches of various colors (e.g., brown, salmon, pink, or white) can occur on the trunk, abdomen, neck, and face. The diagnosis is clinical and is confirmed with KOH examination, which shows fungal hyphae and budding. Management includes topical or oral antifungal medications.
  • Secondary syphilis: STI caused by Treponema pallidum: Secondary syphilis presents after the primary stage (chancre) with a maculopapular rash (including the palms and soles), fever, and lymphadenopathy. Systemic manifestations are common and are not seen in pityriasis rosea. The diagnosis is established through nontreponemal and treponemal testing. Penicillin G is the antibiotic of choice in management.
  • Guttate psoriasis: variant of psoriasis: Guttate psoriasis is an immune-mediated inflammatory skin condition. This form of psoriasis presents with small, salmon-colored papules that look like dewdrops on the skin. The trunk and extremities are commonly involved. No herald patch precedes this eruption. The diagnosis is clinical, and management includes topical corticosteroids, calcitriol, and phototherapy. 
  • Atopic dermatitis: a chronic, relapsing, inflammatory skin condition: Patients present with pruritic, erythematous, thickened, scaly patches that frequently affect flexural regions. This distribution and the chronicity of the condition differentiates atopic dermatitis from pityriasis rosea. The diagnosis is clinical. Management focuses on avoiding potential triggers, topical steroids, and immunosuppressive therapy.

References

  1. Goldstein AO, Goldstein BG (2020). Pityriasis rosea. In Ofori AO (Ed.), UpToDate. Retrieved February 22, 2021, from https://www.uptodate.com/contents/pityriasis-rosea
  2. Das S (2020). Pityriasis rosea. MSD Manual Professional Version. Retrieved February 25, 2021, from https://www.msdmanuals.com/professional/dermatologic-disorders/psoriasis-and-scaling-diseases/pityriasis-rosea
  3. Litchman G, Nair PA, Le JK (2020). Pityriasis rosea. StatPearls. Retrieved February 25, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK448091/
  4. Schwartz RA, Janniger CK, Lichenstein R (2021). Pityriasis rosea. In Elston DM (Ed.), Medscape. Retrieved February 25, 2021, from https://emedicine.medscape.com/article/1107532-overview

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