Pityriasis Rosea

Pityriasis rosea is a mild, acute inflammatory disease of the skin, characterized by a pink rash on the trunk, arms, and legs. The rash may also appear on the neck, and rarely on the face.

The rash usually first appears as a large, pink patch (which may be scaly in texture) on the chest or back. This first patch is called the herald patch or the mother patch. One to 2 weeks after the appearance of the mother patch, more pink patches will appear. Like the mother patch, they are pink, often scaly, and oval. After a period of 2 to 10 weeks, the rash disappears on its own (spontaneously). Rarely, pityriasis rosea may be localized to a specific region of the skin.

The cause of this disease is unclear, and although the current thinking is that it might have an infectious origin, no specific infectious agent responsible for the disease has been identified to date. It is not caused by a fungus, bacteria, or allergy. Some scientists have suggested it might be caused by a virus, but this has not been proven. Based on antibody studies, human herpesvirus-6 and human herpesvirus-7 may be involved in some individuals. It is similar to rashes caused by infections (infectious exanthems) in that household contacts of individuals with the condition are at increased risk; there is a seasonal tendency for it to occur in the spring, winter, and fall; and there is a low rate of recurrence. Other scientists suggest this disease might be caused when an individual's immune system attacks its own tissues (autoimmune disease), but this theory has not been proven either. Drug-induced pityriasis rosea may be caused by captopril, gold, bismuth, barbiturates, isotretinoin, and a few other drugs.

Risk Pityriasis rosea usually affects adolescents and young adults. The peak age of onset falls between 10 and 35 years of age, with a mean age of 23 {Ferri 664}. However, individuals of any age can be affected.

The disease seems to occur equally among various races. It occurs slightly more frequently in women than men, at a ratio of 1.5 to 1 {Ferri 664}. There does not appear to be a strong hereditary link, as fewer than 5% of individuals report a family history of this condition.

Incidence and Prevalence Pityriasis rosea is a relatively common disease, estimated to affect 0.13% of men and 0.14% of women; approximately 0.3% to 3.0% of individuals attending dermatology clinics have this condition {Lichenstein}.

History Rash is often the only symptom, with itching (pruritus) in 75% of cases. Itching is usually mild and rarely severe. Some individuals may have symptoms preceding the onset of the disease, which include a general feeling of illness (malaise), fever, headache, fatigue, sore throat, loss of appetite (anorexia), nausea, and joint pain.

Physical exam The rash consists of rosy pink, oval patches (lesions), with fine scales in the middle and loose scales around the border of each lesion. The first lesion to appear (herald patch) is usually 2 to 10 cm in diameter, but the subsequent (and more numerous) lesions are smaller, about 5 to 10 mm in diameter. These secondary lesions are symmetrical, and follow lines of skin cleavage, typically making a Christmas tree pattern on the back. The rash most commonly appears on the torso, arms, and legs, less frequently on the neck, and rarely on the face. In atypical pityriasis rosea, which occurs in about one-fifth of individuals, the herald patch may be missing or may blend into the secondary lesions. There may be associated lesions in the mouth (oral). If the individual is seen after the inflammatory stage of the disease has occurred, changes in skin color may be noted—either darkening or lightening of the skin (in blacks, darkening of the skin may be more frequent).

Tests The diagnosis is usually based on the physical examination and the individual's symptoms. However, blood tests may be conducted to rule out other conditions, such as autoimmune disease or syphilis. Often, the physician will perform a potassium hydroxide (KOH) test to distinguish pityriasis rosea from another skin condition called ringworm (tinea corporis). A skin biopsy may be needed to confirm the diagnosis but is not usually recommended.

Pityriasis rosea will go away (resolve) on its own (spontaneously) without treatment. The skin should be kept clean to avoid infection. Artificial and natural sunlight seem to help clear up the rash, but this approach should be used with caution due to the potentially harmful effects of ultraviolet light, such as sunburn and skin cancer. Many doctors prefer to let the rash go away naturally over time. Itching may be relieved by lukewarm oatmeal baths or by itch-relieving medication (antipruritics, antihistamines, steroids) applied directly to the skin (topically) or taken by mouth (orally). A recent study showed that oral erythromycin was effective in three-fourths of individuals.

Pityriasis rosea gradually resolves over 1 to 14 weeks (usually 2 to 6 weeks). Complete recovery is expected, and recurrence is rare (less than 3%).

Most individuals will not require restrictions or accommodations. Because sweating will aggravate itching, strenuous activity or working outdoors in warm temperatures should be avoided until the rash clears. Chemicals that may not normally be irritating (soap, for example), might irritate the rash of an individual with this condition. If the job requires contact with such chemicals, protective clothing may be required. Certain medications (antihistamines) that may be prescribed to relieve itching can also cause drowsiness. In such cases, individuals using these medications should avoid operating heavy machinery, driving, or performing work where alertness is required. In cases in which alertness is absolutely required to be able to do the job, individuals should ask their health care provider to prescribe an alternative, nonsedating antihistamine drug.

Pityriasis rosea is generally uncomplicated. However, secondary infection of the skin lesions can occur.

The length of disability varies, depending on the severity of the individual's symptoms; the response to treatment, if any is indicated; and the natural course of this condition. If the individual develops a secondary infection, the period of disability will be longer.

Pityriasis rosea typically resolves without treatment.

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

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