Introduction
Background
Pityriasis rosea (PR) is a common benign papulosquamous disease that was originally described by Camille Melchior Gibert in 1860. Pityriasis denotes fine scales, and rosea translates as rose colored or pink. Pityriasis rosea can have a number of clinical variations. Its diagnosis is important because it may resemble secondary syphilis.
Pathophysiology
Pityriasis rosea has often been considered to be a viral exanthem. Its clinical presentation supports this concept. Pityriasis rosea has been linked to upper tract respiratory infections, it can cluster within families and close contacts, and it has an increased incidence in individuals who are immunocompromised. As with viral exanthems, the incidence may increase in the fall and the spring. A single outbreak tends to elicit lifelong immunity.
Immunologic data suggest a viral etiology. Increased amounts of CD4 T cells and Langhans cells are present in the dermis; this observation may indicate viral antigen processing and presentation. Also, anti-immunoglobulin M (IgM) to keratinocytes has been found in patients with pityriasis rosea; this finding may be associated with the exanthem phase of the presumed viral infection.
Despite these tendencies, no single virus has been proven to cause the disease. A number of viruses have been studied for a link to pityriasis rosea. Picornaviruslike particles have been seen in the tissue of African green monkeys inoculated from human pityriasis rosea lesions. A follow-up study failed to find picornavirus RNA in patients with pityriasis rosea. Serology and polymerase chain reaction for viral DNA have been negative for Epstein-Barr virus, parvovirus B19, cytomegalovirus, human herpesvirus (HHV) – 8,1 HHV-1, and HHV-2 in patients diagnosed with pityriasis rosea.
Other work demonstrated HHV–7 viral DNA in both the lesions and the plasma in patients with pityriasis rosea.2 In addition, a separate study found HHV-7 DNA in lymphocytes in 75% of patients with pityriasis rosea, compared with 9% of controls. Polymerase chain reaction has shown both HHV-7 and HHV-6 DNA in a variety of tissues and secretions from patients with pityriasis rosea. In the same study, in situ hybridization of lesional lymphocytes showed both HHV-7 and HHV-6 mRNA. However, herpesviruslike particles were not seen via electron microscopy.3 Follow-up studies have not confirmed a herpes etiology, and because HHV-7 is frequently found in healthy individuals, its etiologic role is controversial.
Frequency
International
Worldwide, pityriasis rosea has been estimated to account for 2% of dermatologic outpatient visits. The disease is more common in the spring and the fall in temperate climate zones. However, it may be more frequent in the summer in some other regions, and it favors the hot, dry season in Australia, India, and Malaysia.
Mortality/Morbidity
Pityriasis rosea is a benign self-limited disease associated with mild morbidity with rash and occasional pruritus. It has been associated with neonatal hypotonia, hyporeactivity, and premature delivery. An increased risk of miscarriage may occur, especially mothers who developed pityriasis rosea within the first 15 weeks of their pregnancy.4
Race
No racial predominance is reported. More intensely pigmented Africans tend to have more widespread disease. The lesions in African Americans may lack a rose color, and they may appear darker than the surrounding skin.
Sex
Pityriasis rosea is more common in women than in men.5 One study found it to be twice as common in women as in men.
Age
Pityriasis rosea commonly develops in children and young adults, although any age group can be affected. Most patients are aged 10-35 years.
Clinical
History
The history should include questions about close contacts with similar eruptions. This finding is uncommon because most cases of pityriasis rosea are sporadic, as pityriasis rosea is thought to reflect a weakly contagious disease. A history of medication intake should be obtained because several medications have been shown to cause a similar exanthem.
- The disease typically begins with a solitary macule that heralds the eruption (called the herald spot/patch), which is usually a salmon-colored macule. This initial lesion enlarges over a few days to become a patch with a collarette of fine scale just inside the well-demarcated border.
- Within the next 1-2 weeks, a generalized exanthem usually appears, although it may occur from hours to months after the herald patch. This secondary phase consists of bilateral and symmetric macules with a collarette scale oriented with their long axes along cleavage lines. This phase tends to resolve over the next 6 weeks, but variability is common.
- Pruritus is common, usually of mild-to-moderate severity, and it occurs in 75% of patients.
Physical
- The herald patch is usually a single pink patch, 2-10 cm in diameter, on the neck or the trunk with a fine collarette scale (see Media File 1). It is observed in more than 50% of patients, and it may occur as multiple lesions or in atypical locations.
- About 1-2 weeks after the herald patch is seen, the generalized eruption appears, although it has been known to occur from hours to 3 months later. It consists of salmon-colored macules or patches, 0.5-1.5 cm in diameter, with a collarette scale, often described as having a cigarette paper–like appearance. The long axes of the lesions are oriented in a parallel fashion along cleavage lines, giving the classic Christmas tree pattern (see Media File 2). These secondary lesions most commonly occur on the trunk, the abdomen, the back, and the proximal upper extremities.
- Pruritus occurs in 75% of patients and is severe in 25%.
- Lymphadenopathy is uncommon, but, when present, it is usually observed in African Americans.
- Atypical pityriasis rosea occurs in 20% of patients.
- These variations can be separated into changes in the lesions and/or their distribution. Variable distribution can be difficult to evaluate.
- Photosensitivity may occur. Photoexacerbated and photoprotected forms have been documented, although photosensitivity is not a classic manifestation of the disease.
- Lesions may be localized to single areas, such as the abdomen, the groin, the axilla, the distal extremities, the palms, and the soles.
- An inverse pityriasis rosea may be seen. This form manifests as lesions on the face and the distal extremities, and it is more common in children than in adults. The herald patch may be the only manifestation of the disease.
- A unilateral variant in which the lesions do not cross the midline has been described.
- Drug-induced cases are frequently observed without the herald patch.
- Variations in lesion morphology are noteworthy.
- Atypical, large patches tend to be fewer in number. They may coalesce to form a variant known as pityriasis circinata et marginata of Vidal. The primary lesions may be papules, vesicles, pustules, or urticarial or purpuric plaques. Pityriasis rosea may first be evident with widespread, intensely pruritic papulovesicles in an unusual distribution, such as on the neck and the scalp.
- Papular pityriasis rosea tends to have scaling papules in the normal distribution; this form is more common in children than in adults.
- Erythema multiforme–like plaques may be evident.
- Oral involvement may occur as punctate hemorrhages, ulcers, papulovesicles, bullae, or erythematous plaques. Most studies find the incidence to be less than 10%; however, one study reported them in as many as 16% of patients.
- Purpuric pityriasis rosea is seen in both adults and children, and it follows the usual presentation of the disease.
- African American children may have more frequent papular lesions and facial and scalp involvement than is usually described. Also of interest is that many patients have resolution of lesions within 2 weeks.6
Causes
Pityriasis rosea may represent a viral exanthem (and at times enanthem).
- Pityriasis rosea–like drug eruptions may be difficult to distinguish from non–drug-induced cases. Medication-induced eruptions have been reported with captopril, metronidazole, isotretinoin, penicillamine, levamisole, bismuth, gold, barbiturates, ketotifen, clonidine, aspirin, and omeprazole. A single case has been reported with terbinafine. Imatinib mesylate has also been implicated.
- Certain vaccinations, such as the BCG vaccine or the diphtheria vaccine, have been reported to cause similar eruptions.
- Lesions are also thought to be increased in individuals with high stress levels.
More on Pityriasis Rosea |
 Overview: Pityriasis Rosea |
| Differential Diagnoses & Workup: Pityriasis Rosea |
| Treatment & Medication: Pityriasis Rosea |
| Follow-up: Pityriasis Rosea |
| Multimedia: Pityriasis Rosea |
| References |
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References
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Further Reading
Keywords
pityriasis rosea benign papulosquamous disease, herald spot, herald patch, picornavirus, human herpesvirus-6, HHV-6, human herpesvirus-7, HHV-7
