Pityriasis rosea is a mild self-limited skin disease of unknown etiology that classically presents with a single erythematous herald patch that is followed with the appearance of a collection of smaller patches. The rash typically lasts for between two and twelve weeks and is usually associated with only a mild degree of pruritis.
A herald patch of pityriasis rosea which started before the rest of the lesion and was initially mistaken for a fungal infection
- Pityriasis rosea presents most often in patients between the ages of 10 and 35 years of age, though case reports indicate the presence of the disease in patients of all ages.
- The disease is geographically unrestricted and appears throughout the year, with a modest increase in frequency in the spring and fall.
- The pathophysiology of pityriasis rosea is poorly understood. The disease is believed to be viral in origin, given the way in which cases cluster in space and time as well as the low rate of recurrence. The responsible microbiologic agent has yet to be identified, though in recent year significant attention has been directed toward a possible role played by human herpes viruses six and seven. In addition, some cases of pityriasis rosea have been linked to drugs such as captopril and clonidine and to the BCG and diptheria toxoid vaccines.
- The initial presentation of the disease is in most cases marked by the appearance of a herald patch, a well-circumscribed erythematous patch multiple centimeters in diameter with mild central clearing and depression. This patch is often confused with tinea corporis. If necessary, the two conditions can be distinguished with a KOH preparation with pityriasis rosea indicated by an absence of hyphae. The reported rate of occurrence of the herald patch ranges from as low as fifteen percent of cases to as high as eighty five percent, with a majority of studies asserting a probability of presentation of roughly eighty percent. Recognition of a prior herald patch is thus not necessary to arrive at a diagnosis of pityriasis rosea.
- The secondary presentation of the disease appears typically within three weeks of the herald patch with the eruption of a multitude of spherical, pink patches between five and fifteen millimeters in diameter with a bilaterally symmetric distribution. These patches resemble the herald patch but are smaller in diameter. They are typically aligned parallel to the slope of the ribs in a distribution that resembles the shape of a Christmas tree. The rash typically spares the hands and feet. It remains present for between two and twelve weeks. There is frequently a degree of associated pruritis. Mild constitutional symptoms are seen in a significant percentage of patients in the form of malaise, nausea, headache, irritability, and gastrointestinal and respiratory symptoms. Joint pain, sore throat, and fever are seen less frequently.
- Atypical presentations are seen in as many as one fourth of all patients. An inverse presentation is the most common variant with involvement of the rash in the face, groin, and axilla. Oral lesions are seen in a significant minority of patients. Case reports indicate the potential for the rash associated with pityriasis rosea to take on a multitude of different forms.
Pityriasis rosea on the back
showing a "christmas tree" pattern
- The diagnosis is based upon clinical findings. Biopsy is only occasionally necessary to provide further support for a diagnosis. There are no specific laboratory findings that can be used to assure a definitive diagnosis.
- Pityriasis rosea is most often confused with tinea corporis. The disease must also be differentiated from atopic dermatitis, syphilis, tinea versicolor, guttate psoriasis, nummular eczema, and pityriasis lichenoides chronica.
- Treatment is unnecessary as the rash resolves on its own within one to three months with minimal associated morbidity.
- Reassurance and patient education are of primary importance, with the patient and family informed of the long duration of the rash and of the lack of any need to alter daily activities in response to it.
- Topical steroids and antihistamines may be of use if there is significant associated pruritis.
- Pregnant women constitute the only patient population placed at significant risk by pityriasis rosea, with infection during pregnancy found to be associated with a high risk of premature delivery and fetal demise. Pregnant patients diagnosed with pityriasis rosea should be referred to a maternal-fetal medicine specialist.
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- Ginsburg, Charles. Pityriasis Rosea. Pediatrics Infectious Disease Journal. November 1991.
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