What rash is associated with a herald patch?

Pityriasis Rosea is Associated with a Herald Patch

Pityriasis rosea is the rash that is classically associated with a herald patch, which appears as the initial lesion before the development of the characteristic widespread secondary eruption. 1, 2, 3

Clinical Features of Pityriasis Rosea

Herald Patch Characteristics

• Appears as a single, large (2-10 cm) erythematous or salmon-colored oval/round patch
• Features an elevated border with a depressed center
• Typically located on the trunk (chest, back, or abdomen)
• Precedes the generalized rash by 1-2 weeks in approximately 80% of cases 1
• May be misdiagnosed as eczema, ringworm, or other dermatological conditions 3

Secondary Eruption

• Develops 4-14 days after the herald patch
• Consists of multiple smaller (0.5-1 cm) oval lesions
• Lesions have a delicate collarette of scales at the periphery
• Distributed in a characteristic pattern:
  • "Christmas tree" pattern on the back
  • "V-shaped" pattern on the upper chest
  • Follows Langer's lines of cleavage (skin tension lines) 2

Pathophysiology and Epidemiology

• Most commonly affects individuals between 10-35 years of age, with peak incidence during adolescence 1
• Associated with human herpesvirus (HHV)-6 and HHV-7 reactivation in many cases 4
• Prodromal symptoms may occur in approximately 5% of patients:
  • Headache, fever, malaise, fatigue
  • Anorexia, sore throat
  • Enlarged lymph nodes, arthralgia 1

Diagnostic Considerations

Key Diagnostic Features

• Presence of the herald patch (though rarely may present with multiple herald patches) 2
• Characteristic distribution pattern of secondary lesions
• Self-limiting course (typically resolves within 6-8 weeks)

Differential Diagnosis

• Secondary syphilis (important to exclude)
• Tinea corporis (ringworm)
• Seborrheic dermatitis
• Nummular eczema
• Drug eruptions
• Lichen planus
• Viral exanthems 3

Management Approach

1. Reassurance about the self-limiting nature is the primary approach for most patients
2. For symptomatic relief:
   • Antihistamines for pruritus
   • Topical corticosteroids for inflammatory lesions
3. For severe or persistent cases:
   • Oral acyclovir may shorten disease duration
   • Ultraviolet phototherapy can be considered (though risk of hyperpigmentation exists) 3, 5
4. Special consideration for pregnant women with pityriasis rosea due to potential association with pregnancy complications 3

Atypical Presentations

• In rare cases, the herald patch may be the only manifestation of pityriasis rosea, representing an abortive form of the disease with a shorter duration 4
• Multiple herald patches have been reported in some cases 2
• Variations in distribution, morphology, and severity can occur

Pityriasis rosea is typically a clinical diagnosis based on the characteristic appearance and evolution of the rash, with the herald patch serving as a key diagnostic feature that helps differentiate it from other papulosquamous disorders.