Pityriasis Rosea

玫瑰糠疹的躯干; photo courtesy of Gary W. Cole, MD, FAAD

• Pityriasis roseais a skin condition that begins as a single, large pink oval-shaped patch found on the trunk of the body called the "herald patch."
• The herald patch is followed one to two weeks later with a profusion of smaller scaling pink lesions on the torso.
• Pityriasis roseais mildlyitchyin 50% of cases and clears spontaneously in an average of six to nine weeks.
• Pityriasis roseais sometimes accompanied by mild,flu-like symptoms.
• Pityriasis roseais not caused by or known to be associated with the common types of theherpesvirus that cause genital,oral herpes, orvaricella(chickenpox).
• Pityriasis rosea has no long-lasting health effects and is not overtlycontagious.
• It is unusual for an individual to have a second episode of skin disease.
• Pityriasis rosea typically occurs in healthy young adults.

Pityriasis rosea characteristically begins as an asymptomatic single, large pink, scaly plaque called the "herald patch" or mother patch, measuring 2-10 centimeters.

Pityriasis rosea is a common viral infection that usually affects individuals between 10-35 years of age. Therashtypically 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 diffuserashof the disease that occurs in people with brown or dark skin may develop either a gray, dark brown, or black coloration.

In addition, after the lesions heal, there may be areas of hypopigmentation and/orhyperpigmentation(lighter or darker patches). These skin changes are sometimes difficult to identify and may lead to a delayed 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). Thisrashis usually limited to the trunk, arms, and legs. Pityriasis rosea usually spares the face, hands, andfeet.

• 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.

The exact cause of pityriasis rosea remains unknown. Most recently, pityriasis rosea has been associated most strongly with a virus from the humanherpesfamily 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, orvaricella(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 immediatelycontagiousto close contacts or health care providers exposed to therash. Most people with known exposure to pityriasis rosea do not seem to contract the rash.

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

• Mild, intermittentitchingis reported in about 50% of individuals affected, especially when peopleexerciseor take hot showers.
• Itchingseems to increase withstress.
• Rarely, it is accompanied byflu-likesymptoms, such assore throat,fatigue,nausea, aching, anddecreased 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 on the basis of 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 secondarysyphilis, which also may mimic pityriasis rosea. In some cases, askin biopsymay be required to rule out otherskin conditions.

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

Pityriasis rosea may be misdiagnosed aspsoriasis,eczema, fungal infection (tinea corporis), secondarysyphilis, drug eruption (a diffuse body rash caused commonly by a reaction to a medications like an oral antibiotic),fixed drug eruption(a single small, circular or oval patch of skin rash caused by taking a medication),pityriasis lichenoideschronica, parapsoriasis, orlichen 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 isitching, which can be treated withover-the-counter局部类固醇乳霜(如氢化可的松cream) and oralantihistamines(likediphenhydramine[Benadryl],cetirizine[Zyrtec]). These will not shorten the duration of the rash but will decrease theitching. Another treatment for itching is ultraviolet light (UVB) or sunlight. Generally, the best treatment is to avoid being overheated by reducingexerciseand avoiding hot showers and baths.

There has been limited evidence of reduced duration of pityriasis rosea with the off-label use of the antibioticerythromycinor off-label use of antiviral medications such asacyclovir(Zovirax) orfamciclovir(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 of 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-itchlotions 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 inpregnancy, within the first 15 weeks, there seems to be a greater chance ofmiscarriage. 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 withacyclovir.

There is no definitivepreventionfor pityriasis rosea, as the cause is not yet fully known.

• 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-lastingscars, although some mild, temporary skin discoloration called post-inflammatory hypopigmentation orhyperpigmentationcan 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 preventoverheating.
• Once a person has pityriasis rosea, they generally have lifelong immunity.

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