Continuing Education Activity

A herald patch is a distinct skin manifestation characterized by a single, erythematous, round to oval scaly patch or plaque. The patch has a depressed center and raised border and measures 2 to 10 cm. The lesion typically exhibits a predilection for the neck, chest, and back. As the lesion evolves, it tends to clear centrally, leaving the free edge of the scale. This reveals a unique "collarette" of scale, which is a common presenting sign of pityriasis rosea—a prevalent and self-limiting papulosquamous disorder. This clinical presentation resembles the edge of a cigarette paper directed inward toward the center.

The sign is called the "herald" patch or "mother" patch because it often appears a few days to 2 weeks before the complete eruption of pityriasis rosea. This activity reviews the etiology and evaluation of pityriasis rosea, emphasizing the importance of the interprofessional healthcare team in treating patients with herald patches. This activity highlights the roles of participating clinicians in assessing the rash distribution, frequency, and progression predictability, with optimal coordination among primary care and dermatology consultation as necessary.

Objectives:

• Identify the characteristic features of a herald patch, including its single, erythematous, round to oval scaly appearance with a depressed center and raised border. 

• Screen patients presenting with skin abnormalities for the presence of a herald patch to facilitate early recognition and intervention.

• Apply evidence-based guidelines and clinical protocols in assessing and managing herald patches and suspected pityriasis rosea.

• Coordinate follow-up care and referrals as necessary, ensuring continuity of care and monitoring for potential complications or recurrences in patients with herald patches.

Introduction

A herald patch is a distinct skin manifestation characterized by a single, erythematous, round to oval scaly patch or plaque. The patch has a depressed center and raised border and measures 2 to 10 cm (see Image. Herald Patch). The lesion typically exhibits a predilection for the neck, chest, and back. As the lesion evolves, it tends to clear centrally, leaving the free edge of the scale. This reveals a unique "collarette" of scale, which is a common presenting sign of pityriasis rosea—a prevalent and self-limiting papulosquamous disorder. This clinical presentation resembles the edge of a cigarette paper directed inward toward the center.

The sign is called the "herald" patch or "mother" patch because it often appears a few days to 2 weeks before the complete eruption of pityriasis rosea.[1][2][3][4] In 10% to 50% of the cases of pityriasis rosea, the herald patch may be absent, especially in drug-induced cases. On the other hand, the herald patch may appear in multiple locations and atypical sites, such as the soles or scalp. In some cases, the skin patch is the sole manifestation of the disease, not followed by a secondary rash.

Etiology

The herald patch and pityriasis rosea are thought to be caused by infection with human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7), but this is debatable. Evidence supporting an infectious etiology includes outbreaks occurring in clusters, the prodromal symptoms in most patients before the herald patch or eruption of pityriasis rosea occurs, and the rare instance of recurrence that suggests immunity. Human herpesvirus 8 (HHV-8), the 2009 to 2010 pandemic H1N1 influenza A virus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported in association with pityriasis rosea.[5][6][7][8]

In one retrospective cohort study, pityriasis rosea only recurred in 3.7% of patients, but none of these recurrences manifested with a herald patch. Interactions between Langerhans cells, unknown components of the epidermis, and dermal dendritic cells have also been postulated, but whether these interactions are due to a viral etiology is still uncertain.[9][10][11] Pityriasis rosea has also been linked with vaccinations for smallpox, tuberculosis, influenza, papillomavirus, polio, tetanus, diphtheria, pneumococcal, diphtheria-pertussis-tetanus, hepatitis B, and yellow fever [12] and more recently with the COVID-19 vaccines.[13][14] Pityriasis rosea-like eruptions can also occur in association with many drugs, such as acetylsalicylic acid, barbiturates, bismuth, captopril, clonidine, gold, imatinib, isotretinoin, ketotifen, levamisole, metronidazole, omeprazole, D-penicillamine, and terbinafine.[15]

Epidemiology

The herald patch is seen in approximately 80% of the cases of pityriasis rosea. The incidence of pityriasis rosea peaks between 20 and 29, but it may be seen in any age group. Pityriasis rosea occurs slightly more in females than in males.[16] The disease is more common in the spring and the fall in temperate climate zones. No racial predominance is reported. Nonetheless, intensely pigmented Africans tend to have more widespread disease, with lesions darker than the surrounding skin, unlike the rose color seen in other patients with fair complexion.

Pathophysiology

The pathophysiology of pityriasis rosea, and thus the herald patch, is poorly understood. As stated, an association with HHV-6 and HHV-7 is recognized in the plasma and lesional skin of patients with pityriasis rosea, but other studies have revealed conflicting evidence. The inflammatory populations seen in lesions of pityriasis rosea and the herald patch are predominantly T cells with a lack of B cells and natural killer cells. Natural killer cells are cytotoxic to cells infected with viruses, and their presence is suspected if it is solely due to a viral etiology. Interactions between the Langerhans cells and unknown components of the epidermis have been implicated in the pathophysiology, but this is not fully understood.

Histopathology

The immunohistochemical and histopathological findings in the herald patch and fully developed lesions of pityriasis rosea are similar. Histological findings of pityriasis rosea include focal or confluent parakeratosis, epidermal hyperplasia, spongiosis, exocytosis of lymphocytes, and extravasation of erythrocytes along with a moderately dense perivascular lymphocytic infiltrate in the superficial dermis. Due to its chronic nature, the herald patch has similar features but a deeper infiltrate and more acanthosis.

Some other variations have been observed, such as dyskeratotic cells in the epidermis, multinuclear giant cells, and focal acantholytic dysfunction. These features may closely resemble erythema annulare centrifugum, guttate psoriasis, superficial gyrate erythema, and small plaque parapsoriasis. Immunohistochemical analysis usually reveals an increased CD4+ to a CD8+ ratio of T lymphocytes, and increased numbers of Langerhans cells have been observed in specimens.

History and Physical

The herald patch is a round to oval erythematous patch or plaque with central clearing and peripheral scale trailing behind the margins of the erythema. The herald patch typically measures 2 to 10 cm. However, rare reports of very large herald patches have been described, with one case nearly covering the entire trunk of an 18-month-old female child.[17] Most herald patches appear on the trunk, neck, or proximal extremities, although in rare cases, they have appeared on the face, genitalia, scalp, and acral surfaces. Most lesions are asymptomatic, but some may be pruritic.

Most patients experience prodromal symptoms, including a headache, fever, arthralgias, and malaise before or around the time the herald patch appears. A few days to 2 weeks after the appearance of the herald patch, patients develop a more diffuse eruption of pityriasis rosea. This is accompanied by smaller lesions resembling the herald patch along skin cleavage lines in a "Christmas tree" or "fir tree" distribution, with truncal predominance. The lesions are sometimes atypical in children; they may be follicular-papular, pustular, vesicular, urticarial, or purpuric.[18] The eruption spreads from the top down over a few days. The eruption fades in 4 to 6 weeks, leaving few residual changes, such as postinflammatory dyspigmentation. Oropharyngeal abnormalities have been reported in patients with pityriasis rosea in the form of petechial, macular, and papular eruptions.[19] A proposed classification divides pityriasis rosea into classic, relapsing, persistent, pediatric, pityriasis rosea in pregnancy, and pityriasis rosea–like eruptions.[20]

Evaluation

A definitive diagnosis of the herald patch can be difficult before the classic eruption of pityriasis rosea. Typically, no laboratory abnormalities in pityriasis rosea are expected. Due to the morphological similarities with tinea corporis, a potassium hydroxide (KOH) examination of scales for dermatophyte hyphae may be necessary to distinguish these conditions. If the potassium hydroxide examination is equivocal, a biopsy may be performed, which may aid in differentiating the herald patch from tinea, erythema annular centrifugum, or nummular eczema. When the full eruption of pityriasis rosea finally presents, the palms and soles should be checked for involvement, as the eruption can mimic secondary syphilis. If secondary syphilis cannot be ruled out, nontreponemal tests such as the rapid plasma reagin test should be performed with appropriate confirmatory tests.[21][22][23][24]

Treatment / Management

Because the herald patch is a feature of pityriasis rosea, the same treatment is advised for both. The eruption of pityriasis rosea is a benign, self-limited papulosquamous process. No treatment is necessary, and the eruption of both the herald patch and pityriasis rosea should resolve within 8 weeks. Patients typically seek treatment for pruritis that occasionally is associated with pityriasis rosea, or because the appearance of the rash perturbs them. Most cases of pityriasis rosea are asymptomatic or minimally pruritic, but approximately 25% of patients experience severe pruritis.

If the lesions are symptomatic or disturbing, the following guidance is beneficial:

• Patients and their caregivers should be reassured that pityriasis rosea typically resolves within 2 to 3 months with low risk for transmission, and recurrence is uncommon. Patients should also be instructed to avoid scratching and contact with irritants, such as harsh soaps, synthetic fabrics, fragrances, hot water, tight clothing, and sweating.

• Topical steroids in the medium potency range should be applied to the pruritic areas 2 to 3 times per day for 2 to 3 weeks, under medical supervision, to avoid corticosteroid-induced skin atrophy that could result from long-term use.

• Topical antipruritic lotions that contain pramoxine, menthol, calamine lotion, or zinc oxide may help to reduce pruritus.[25]

• Oral antihistamines can reduce the irritation and help the patients sleep better at night.

• Oral steroids may also improve the pruritus of pityriasis rosea; however, routine use is not recommended due to limited data on their efficacy and concerns of relapse after treatment.[26]

• The postulated link between pityriasis rosea and human herpes viruses led to the investigation of oral acyclovir in patients with pityriasis rosea. However, high-quality studies are still lacking, and the rationale for its benefit remains unclear.[27]

• Ultraviolet B phototherapy and a 2-week course of oral erythromycin have been shown to shorten the duration of the eruption.[28][29][28]

• UVA1 phototherapy is associated with reduced disease severity and improvement in pruritus.[30]

• Trials of clarithromycin and azithromycin for pityriasis rosea support the inefficacy of these therapies.[31][32][31]

Differential Diagnosis

The differential diagnosis of the herald patch differs from pityriasis rosea because the former is a single lesion while the latter is an eruption. The differential diagnosis for the herald patch includes tinea corporis, nummular eczema, and erythema annulare centrifugum. A helpful distinguishing feature among most of these conditions is the location of the scale within the erythema. The herald patch and erythema annulare centrifugum often exhibit a trailing scale. This is seen as a collarette of scale inside the borders of the erythema. The edge of the scale in tinea appears to lead the erythema in an annular fashion. Nummular eczema typically has scale throughout the lesion without central clearing.

When herald patch evolves into the complete picture of pityriasis rosea, the differential diagnosis should include secondary syphilis, guttate psoriasis, tinea versicolor, and pityriasis lichenoides chronica. Lyme disease, HIV, seroconversion illness, and drug eruptions should also be considered in the differential diagnosis of pityriasis rosea. Testing for HIV should be performed in patients with risk factors for or symptoms suggestive of HIV infection.

Prognosis

The eruption of the herald patch and pityriasis rosea should resolve within 8 weeks. Reports of a variant of pityriasis rosea known as persistent pityriasis rosea have been described, with some lasting longer than 12 weeks. The herald patch is seen in most cases, and a higher association with systemic symptoms, oral lesions, and increased HHV-6 and HHV-7 viral loads was found in association. Relapse after a resolution is uncommon (approximately 2%).[33]

Complications

Postinflammatory hyperpigmentation is a common sequela in individuals with darkly pigmented skin and often takes several months or longer to resolve. Research on the impact of pityriasis rosea on pregnancy is limited and conflicting. An analysis of a case series of women who developed the disease during pregnancy suggested that pityriasis rosea increases the risk of spontaneous abortion.[34] However, the frequency of spontaneous abortion is lower in other series and comparable with rates in patients without the disease.[35][36]

An analysis of pooled data from patients in case reports and case series suggested a greater likelihood for unfavorable pregnancy outcomes, such as preterm delivery, low birth weight, or spontaneous abortion, among pregnant individuals with extensive or prolonged course of the disease, onset of eruption earlier in pregnancy, or associated extracutaneous symptoms.[35] However, the timing of the onset of pityriasis rosea did not seem to be a relevant factor for pregnancy complications in another case series.[36] Further studies are necessary to clarify the impact of pityriasis rosea on pregnancy.

Deterrence and Patient Education

Patients affected by the herald patch and its subsequent secondary rash of pityriasis rosea should be educated about the self-limiting and noninfectious nature of the disease. Treatment is mainly supportive to relieve the symptoms of itching. Patients should avoid scratching the lesions and contact with irritants.

Pearls and Other Issues

Herald patch is the first to present a lesion of pityriasis rosea. Although the presentation is unique to pityriasis rosea, it can resemble tinea corporis, discoid eczema, and erythema annulare centrifugum. Within 2 weeks, the distinctive secondary rash of pityriasis rosea develops following the cleavage lines of the skin, forming the "Christmas tree" pattern. This persists for another 2 weeks and resolves over another 2 weeks without needing treatment. Nonetheless, some lesions may persist for 3 to 4 months.

Enhancing Healthcare Team Outcomes

Pityriasis rosea is a commonly encountered skin condition in clinical practice, managed by primary care clinicians, nurse practitioners, dermatologists, and emergency department clinicians. Recognizing the herald patch is crucial, as at least 25% of patients experience severe itching, which, if left untreated, can significantly impact their quality of life. These patients require follow-up as recurrences are possible.[37]