Pityriasis rosea

Are You Confident of the Diagnosis?

In 1798, British physician Robert Willan first described a self-healing cutaneous eruption termed roseola annulata. However, it wasn’t until 1860 that French physician Camille Melchior Gilbert renamed this exanthem pityriasis rosea, the name still currently in use.

Characteristic findings on physical examination

Pityriasis rosea is an acute, self-limited exanthem characterized classically by the eruption of a well-circumscribed, pink, oval, scaling patch, or ‘herald patch’ that is usually several centimeters in diameter. It may have slightly elevated borders, a pale center, and a collarette of scale. The herald patch is typically located on the trunk, followed several days to weeks by a symmetric eruption of smaller similar lesions following Langer’s lines, lasting approximately 1-3 months. A typical course lasts an average of 6-8 weeks.

The eruption is classically described as in a ‘Christmas tree pattern’ because the skin-cleavage lines run diagonally along the back. The herald patch may go unnoticed and usually has resolved by the time the patient seeks medical care. The face, scalp, palms, and soles are typically spared.

Although classically asymptomatic, there may be differing degrees of pruritus as well as a prodrome of constitutional symptoms including malaise, nausea, gastrointestinal and respiratory symptoms, headache, irritability, difficulty in concentration, loss of appetite, joint pain, sore throat, and mild fever. Relapse is uncommon but may occur.

Atypical presentations may make the diagnosis difficult. Patches can be extremely large (pityriasis rosea gigantea of Darier) or minute. Pityriasis rosea can rarely present with different morphologies, including annular lesions mimicking tinea, edematous papules or plaques resembling urticaria (pityriasis rosea urticata), or targetoid lesions resembling erythema multiforme. It can also be vesicular and may present as vesicles arranged in a rosette pattern.

Papular pityriasis rosea, which is more often seen in children, presents with the classic pink oval scaling patches admixed with small papules (Figure 1). In a minority of cases, it may involve the oral mucosa which is more commonly seen in dark-skinned patients. This may present as punctate hemorrhages, erosions, erythematous solid or annular macules, or most commonly ulcerations. Bullous lesions have been described. The mucosal lesions typically follow a similar course as the cutaneous eruption.

Figure 1.

Purpuric pityriasis rosea (Figure 2) has also been reported and may be associated with palatal petechiae.

Figure 2.

Distribution may also lead to difficulty in diagnosis even for the seasoned practitioner. The eruption may be limited to a solitary herald patch, or multiple few large herald patches without the accompanying smaller lesions. Inverse pityriasis rosea can involve the face, scalp, axillae, and inguinal creases, which are not typical locations of classic pityriasis rosea. Unilateral pityriasis rosea has also been described in the literature, as well as a limb-girdle type in which lesions are located on the shoulders or hips. Drug induced pityriasis rosea may occur without a herald patch, be more violaceous in color, and eosinophilia may be present.

Pityriasis circinata et marginata of Vidal may also be included as a form of pityriasis rosea. It was originally described as a few large patches localized to the axillae or inguinal creases, typically in adults lasting several months to years. Involvement of the distal fingers, distal toes, eyelids, and penis has been reported.

In persons of color, notably African patients, the rash is frequently located on the face and scalp, with a higher incidence of oral involvement, and may be more prevalent in the winter months. It may be difficult to appreciate the inflammation, which, can vary from violaceous to grey in color. Inverse and papular variants are more common in this population and they may leave postinflammatory dyspigmentation.

Expected results of diagnostic studies

Diagnosis is based primarily on history and physical examination alone. A skin biopsy may be necessary to support the diagnosis as it can mimic many other conditions. Histologically, there are focal mounds of parakeratosis with exocytosis of lymphocytes and variable spongiosis. Mild acanthosis and a thinned granular layer are also observed. In the dermis there is a perivascular lymphocytic infiltrate with eosinophils and extravasated red blood cells. Monocytes may also be present as well as dyskeratotic keratinocytes in approximately half of the cases.

Diagnosis confirmation

Differential diagnosis of pityriasis rosea includes tinea corporis, tinea versicolor, pityriasis lichenoides chronica, guttate psoriasis, syphilis, nummular eczema, subacute cutaneous lupus erythematosis (SCLE), benign pigmented purpura, atopic dermatitis, digitate dermatoses, cutaneous T-cell lymphoma (CTCL) and pityriasis lichenoides.

Tinea corporis and tinea versicolor are common rashes that can mimic annular pityriasis rosea. A potassium hydroxide (KOH) preparation can easily distinguish these disorders. Pityriasis lichenoides chronica, however, can be differentiated mainly by history as it typically lasts from several months to years and does not commence with a herald patch.

Guttate psoriasis usually presents with thicker micaceous scale and an Auspitz sign. There may also be a history of preceding streptococcal infection in children with guttate psoriasis. If necessary, histologic examination can usually differentiate these disorders.

Secondary syphilis, frequently termed the great imitator, can look identical to pityriasis rosea and may be missed if the physician does not have a high index of suspicion. Syphilis typically involves the palms and soles and does not begin with a herald patch which may aid in the diagnosis. Lymphadenopathy is common in secondary syphilis.

Numerous plasma cells seen histologically and a positive rapid plasma reagin (RPR) and/or treponemal antibody test are useful as well. Of note, the RPR may be falsely negative early in the course of the syphilis secondary to the ‘prozone phenomenon’ from very highly concentrated levels of antibodies.

Lesions of SCLE may also mimic pityriasis rosea; however, they are typically photo-distributed. Serologic and histologic examination can be useful as anti-SS-A/Ro and anti-SS-B/La antibodies are usually positive in SCLE along with basal layer vacuolarization, epidermal atrophy, and Civatte body formation histologically.

Capillaritis can also mimic pityriasis rosea. Most similar clinically is the ‘eczematoid-like purpura of Doucas and Kapetanakis’ variant which may be distinguished by histology.

Nummular eczema is typically located on the extremities and is extremely pruritic. It usually rapidly improves with topical steroids and is often lichenified or thickened from intense rubbing. Histologic examination will show more prominent spongiosis.

Patch stage CTCL, especially presentations with digitate lesions mimicking digitate dermatosis, can easily be mistaken for pityriasis rosea during initial evaluation. Therefore, any eruption that does not respond to topical steroids and lasts longer than three months should be biopsied to rule out CTCL. Unfortunately, multiple repeat biopsies are necessary before CTCL is diagnosed.

Pityriasis lichenoides (PLEVA and PLC) can mimic pityriasis rosea at initial presentation. Typically, pityriasis lichenoides lesions will be papulonecrotic or papulosquamous with more persistent and recurrent lesions. Skin biopsy is helpful in establishing the diagnosis.

Other less commonly confused entities may be entertained, such as seborrheic dermatitis, lichen planus, erythema dyschromicum perstans, and acute HIV infection.

Who is at Risk for Developing this Disease?

Pityriasis rosea often presents between the ages of 10-35 years old; however, it has been reported in infants, young children, and the elderly. There is no geographic predominance. It tends to be seen more frequently in the spring and fall months. There is no racial or sex predilection. Pityriasis rosea has been reported to occur more frequently in pregnancy.

Pityriasis rosea may possibly be associated with an atopic diathesis and may coincide with a number of internal disorders, particularly neurological disorders. This may be due to the tropism of human herpes virus (the possible causative agent of pityriasis rosea) for the central nervous system; however, this has never been validated and is at best controversial.

Pityriasis rosea-like eruptions have been reported with several neoplasms (gastric and bronchogenic), T-cell lymphomas, Hodgkin disease, and bone marrow transplantation. It is unclear if these associations are coincidental or related to reactivation of latent viruses triggered by decreased immunity.

What is the Cause of the Disease?

• Etiology

• Pathophysiology

The pathogenesis of pityriasis rosea is poorly understood. However, given the nature of the disease to occur in ‘outbreaks’ and its low rate of reoccurrence, it is believed there is an infectious agent responsible for the disease that has not been identified. To date, evidence suggests that human herpes virus 6 (HHV-6) or Human Herpes Virus 7 (HHV-7) may possibly play a role in its pathogenesis; however, this is still controversial. The skin lesions may represent a reactive response of systemic viral replication in contrast to direct inoculation. Again, there is no evidence to date to support these claims.

Several medications have been reported to cause a ‘pityriasis rosea-like’ reaction including:

• anti-hypertensives: captopril, clonidine, hydrochlorothiazide, atenolol;

• antipsychotics: asenapine, clozapine, nortriptyline, barbiturates, bupropion;

• biological agents: adalimumab, rituximab;

• antiepileptics: lamotrigine;

• antibiotic/antifungals: metronidazole, pristinamycin, terbinafine;

• metals: arsenic, bismuth, gold;

• other: isotretinoin, non-steroidal anti-inflammatory agents, omiprazole, D-penicillamine, levamisole, pyribenzamine, ergotamine tartrate, pristinamycin, and tyrosine kinase inhibitors. ‘Pityriasis rosea-like’ eruptions have been described after several vaccines including: diphtheria, smallpox, pneumococcal, hepatitis B, H1N1 influenza, yellow fever, smallpox, humanpapillomavirus, and bacillus Calmette-Guérin (BCG).

Systemic Implications and Complications

Pityriasis rosea has been reported to be associated with an increased risk of premature delivery and possible fetal demise during pregnancy, greatest during the first 15 weeks of gestation. Because of this apparent association, it is important that all pregnant women who develop pityriasis rosea be evaluated by a high-risk maternal fetal medicine specialist. Even more importantly, all pregnant patients with pityriasis rosea should be screened for syphilis because of the clinical overlap.

In the general population, there is no systemic involvement of pityriasis rosea and, since it is a self-limited disorder, there are no long-term sequelae. If the exanthem lasts longer than 3 months or there are significant and persistent systemic symptoms, an alternate diagnosis must be entertained.

Treatment Options

Treatment options are summarized in Table I.