Pityriasis Rosea

Pityriasis rosea is mildly itchy in 50% of cases and clears spontaneously in an average of six to nine weeks.

Pityriasis rosea is a common viral infection that usually affects individuals between 10-35 years of age. The rash typically lasts 6-9 weeks, rarely extending longer than 12 weeks. Once a person has pityriasis rosea, it rarely recurs.

Pityriasis rosea characteristically begins as an asymptomatic single, large pink, scaly plaque called the "herald patch" or mother patch, measuring 2-10 centimeters. The herald patch is a slightly scaly dry pink to red plaque that appears on the back, chest, or neck and has a well-defined, scaly border.

Pityriasis rosea in individuals with brown or dark skin color (for example, people with African, Indian, or Hispanic heritage) varies compared with those of Anglo heritage (pinkish coloration). Both the herald patch and the diffuse rash of the disease that occurs in people with brown or dark skin may develop either a gray, dark brown or black coloration.

After the lesions heal, there may be areas of hypopigmentation and/or hyperpigmentation (lighter or darker patches). These skin changes are sometimes difficult to identify and may lead to a delay or misdiagnosis in some patients.

• One to two weeks following its initial appearance, a crop of smaller lesions develop on the trunk, arms, and legs.
• In the second stage of pityriasis rosea erupts with a large number of oval spots, ranging in diameter from 0.5 centimeters (the size of a pencil eraser) to 1.5 centimeters (the size of a peanut). The individual lesions form a symmetrical "Christmas tree" pattern on the back with the long axis of the ovals oriented in the "Lines of Blaschko" (invisible skin lines of embryonic origin). This rash is usually limited to the trunk, arms, and legs. Pityriasis rosea usually spares the face, hands, and feet.

The exact cause of pityriasis rosea remains unknown. Most recently, pityriasis rosea has been associated most strongly with a virus from the human herpes family called human herpesvirus-6 and/or 7 (HHV-6, HHV-7). Pityriasis rosea is not caused by or known to be associated with the common types of the herpes virus that cause genital, oral herpes, or varicella (chickenpox).

While the mode of transmission (how it gets passed between people) of pityriasis rosea is also unknown, respiratory contact has been postulated. Pityriasis rosea does not seem to be directly or immediately contagious to close contacts or health care providers exposed to the rash. Most people with known exposure to pityriasis rosea do not seem to contract the rash.

Pityriasis rosea is, for the most part, equally common in men and women. It generally occurs in children and young adults between 10-35 years of age.

Pityriasis rosea has no racial predominance. Most people only develop pityriasis rosea once in their lifetime.

Picture of pityriasis rosea on the torso; photo courtesy of Gary W. Cole, MD, FAAD

Most people do not notice any symptoms with pityriasis rosea except for the appearance of the rash itself.

• Mild, intermittent itching is reported in about 50% of individuals affected, especially when people exercise or take hot showers.
• Itching seems to increase with stress.
• Rarely, it is accompanied by flu-like symptoms, such as sore throat, fatigue, nausea, aching, and decreased appetite.
• Most people are otherwise in very good health and don't exhibit any other symptoms.

Usually, a doctor may make a diagnosis of pityriasis rosea solely based on its appearance, particularly the onset of the distinct large herald patch and the symmetrical Christmas tree presentation. Also, the herald patch tends to have a fine scale with a definite border, the so-called "collarette."

To rule out other types of skin disorders, a physician may scrape the skin and examine the scales under the microscope to detect fungus infection that could mimic pityriasis rosea.

Also, blood tests including rapid plasma reagent (RPR) may be done to detect secondary syphilis, which also may mimic pityriasis rosea. In some cases, a skin biopsy may be required to rule out other skin conditions.

The first herald patch of pityriasis rosea may look very similar in appearance to ringworm (tinea corporis). Pityriasis rosea has also been mistaken for eczema and psoriasis, which can occur as similar scaly patches, but not in the same distribution as pityriasis rosea.

Pityriasis rosea may be misdiagnosed as the following:

• Psoriasis
• Eczema
• Fungal infection (Tinea corporis)
• Secondary syphilis
• Drug eruption (a diffuse body rash caused commonly by a reaction to medications like an oral antibiotic)
• Fixed drug eruption (a single small, circular, or oval patch of skin rash caused by taking a medication)
• Pityriasis lichenoides chronica
• Parapsoriasis
• Lichen planus

Pityriasis rosea usually is self-limited and requires no treatment and resolves spontaneously. Treatment is not necessary if the rash does not cause significant symptoms. Typically, pityriasis rosea will usually clear on its own within six to nine weeks without medical intervention.

The most common symptom is itching, which can be treated with over-the-counter topical steroid creams (like hydrocortisone cream) and oral antihistamines (like diphenhydramine [Benadryl], cetirizine [Zyrtec]). These will not shorten the duration of the rash but will decrease the itching. Another treatment for itching is ultraviolet light (UVB) or sunlight. Generally, the best treatment is to avoid being overheated by reducing exercise and avoiding hot showers and baths.

There has been limited evidence of the reduced duration of pityriasis rosea with the off-label use of the antibiotic erythromycin or off-label use of antiviral medications such as acyclovir (Zovirax) or famciclovir (Famvir). However, neither of these medications has been proven to be uniformly effective in the treatment of pityriasis rosea and they are not usually necessary or required.

Home remedies for pityriasis rosea include taking lukewarm baths or showers, avoiding drying soaps, wearing cotton or silk clothing to reduce heat, and taking oatmeal baths. Calamine or menthol anti-itch lotions can also be helpful for itching.

The following are additional home remedies:

• Lubricating with bland moisturizers
• Steroid creams (hydrocortisone cream)
• Diphenhydramine (Benadryl) oral pills or liquid for itching
• Natural sunlight exposure to body parts, 10-15 minutes per day

If pityriasis rosea occurs early in pregnancy, within the first 15 weeks, there seems to be a greater chance of miscarriage. In addition, children of affected mothers may be prone to premature delivery. Since there is little that can be done to prevent this disease or treat it, affected mothers are monitored closely for potential problems. Occasionally, healthcare professionals consider treatment with acyclovir.

The prognosis for pityriasis rosea is excellent as the rash is self-limiting and usually clears even without treatment within nine weeks. It typically leaves no long-lasting scars, although some mild, temporary skin discoloration called post-inflammatory hypopigmentation or hyperpigmentation can occur in people with darker skin. It has no known long-lasting side effects and has not been associated with any other diseases.

Symptoms may be reduced with topical treatment or taking extra precautions to prevent overheating. Once a person has pityriasis rosea, they generally have lifelong immunity.

There is no definitive prevention for pityriasis rosea, as the cause is not yet fully known.

A good source of information is the American Academy of Dermatology (http://www.aad.org) or a board-certified dermatologist.