What is the herald patch of pityriasis rosea and how is it managed?

Herald Patch of Pityriasis Rosea: Clinical Features and Management

What is the Herald Patch?

The herald patch is a single, larger erythematous patch that appears on the trunk in approximately 80% of pityriasis rosea cases, typically 4-14 days before the generalized eruption develops. 1

Key Clinical Characteristics

• Size and appearance: The herald patch is 0.5-1 cm or larger, oval or elliptical in shape, presenting as a dull pink or salmon-colored macule with a delicate collarette of scales at the periphery 1
• Location: Most commonly appears on the trunk 1, 2
• Timing: Precedes the secondary eruption by approximately 4-14 days, though this interval can vary 1
• Diagnostic significance: Often misdiagnosed as eczema or ringworm when it appears in isolation 3

Secondary Eruption Pattern

Following the herald patch, a generalized bilateral symmetrical eruption develops over 12-21 days with characteristic features: 1

• Lesions align along Langer's lines (skin cleavage lines) 1
• Creates a "Christmas tree" pattern on the back 1, 2
• Forms a V-shaped distribution on the upper chest 2
• Secondary lesions are typically smaller than the herald patch 1

Rare Variant: Herald Patch as Sole Manifestation

In rare cases, the herald patch may be the only cutaneous manifestation of pityriasis rosea, representing an abortive form of the disease. 4

• This variant shows shorter exanthem duration and lower HHV-6/7 DNA plasma loads compared to classic PR 4
• Occurs when viral reactivation is contrasted by a more robust immunological response 4
• Multiple herald patches can occur, though this is uncommon 2

Differential Diagnosis

When evaluating a suspected herald patch, consider: 1, 2, 3

• Ringworm (tinea corporis): Distinguished by KOH preparation or fungal culture
• Secondary syphilis: Requires serologic testing (RPR/VDRL)
• Erythema annulare centrifugum: Shows different histopathology
• Eczema: Most common misdiagnosis of the herald patch 3
• Drug-induced eruptions: Obtain medication history 3

Management Approach

For Typical Self-Limited Cases

The vast majority of pityriasis rosea cases require only reassurance and symptomatic treatment, as the condition is self-limiting with resolution in 6-8 weeks. 1

• Moisturizers: Apply alcohol-free moisturizers containing 5-10% urea at least twice daily 5
• Sun protection: Use SPF 15 or higher to prevent worsening of hypopigmentation 5
• Symptomatic relief: Topical or systemic antihistamines for pruritus 3
• Low-potency topical corticosteroids: Can be used for inflammation if needed 5

For Severe, Extensive, or Persistent Cases

When active intervention is warranted, acyclovir represents the best option for patients with extensive, persistent lesions or systemic symptoms. 6

• Acyclovir: Most effective for rash improvement (RR 2.55, CI 1.81-3.58 vs placebo), ranked as best intervention (SUCRA 0.92) 6
• Oral steroids: Most effective for itch resolution (RR 0.44, CI 0.27-0.72 vs placebo), SUCRA 0.90 6
• Erythromycin: Significantly superior to placebo for rash improvement (RR 1.69, CI 1.23-2.33), though one small trial showed faster clearing with unclear mechanism 6, 3
• UV phototherapy: May hasten resolution but carries risk of hyperpigmentation 3

Special Populations

Pregnant women with pityriasis rosea warrant active intervention due to potential fetal risks. 1

• Consider acyclovir or erythromycin as safer options during pregnancy 1, 6
• Avoid systemic steroids unless benefits clearly outweigh risks

Clinical Pitfalls to Avoid

• Do not dismiss the herald patch as simple eczema without considering pityriasis rosea, especially in adolescents and young adults 3
• Do not miss secondary syphilis: Always consider serologic testing when the diagnosis is uncertain, particularly if the patient is sexually active 1, 3
• Avoid alcohol-containing preparations: These worsen the xerotic skin characteristic of pityriasis rosea 5
• Do not use aggressive anti-acne treatments: Pityriasis rosea is not seborrheic in nature 5