In many cases, the characteristic rash associated with pityriasis rosea is preceded by vague, nonspecific symptoms similar to those seen with a viral upper respiratory infection. Such symptoms can include fever, headache, stuffy nose, sore throat and fatigue. Sometimes there is no history of preceding illness before the rash appears.
Eventually, affected individuals develop a herald patch, which is a single scaly red patch, usually on the back, chest or stomach. When located on the back the herald patch may go undetected before appearance of the generalized rash. A herald patch is a slightly raised plaque that is usually between 2 to 4 inches large. Often the herald patch is misdiagnosed as ring worm (tinea corporis). Over the next few days or weeks, multiple smaller scaly, pink or red spots will develop. In individuals with darker skin, the rash may be gray, dark brown or black. Although the back, chest and stomach are most commonly affected, the rash may spread to affect the arms, legs and neck. Less often, other areas of the body may become involved. In rare cases, the rash may be isolated (localized) to one specific area of the body. In some people, the rash does not itch; in other people, the rash may be extremely itchy (pruritic).
The rash usually lasts approximately one to three months in approximately 80 percent of cases. Pityriasis rosea eventually goes away on its own, even without treatment, and usually does not leave any scars or permanent marks. People with darker skin may have residual dark spots at sites of inflammation which can last for many months before resolution.
Researchers believe that pityriasis rosea is caused by a viral infection. However, even though the disorder was first described in the medical literature in 1860, no infectious pathogen has ever been identified.
Several factors support the theory that pityriasis rosea is caused by a viral infection – most individuals have vague, nonspecific symptoms before the development of the rash (prodromal illness); after the acute phase of infection the disorder does not recur, suggesting that the body builds up an immunity to the infection; and pityriasis rosea has occurred in clusters, suggesting that a viral illness is affecting a community. Although a virus is believed to cause pityriasis rosea, the disorder is not thought to be contagious.
Some researchers have theorized that autoimmune factors may play a role in the development of pityriasis rosea. Autoimmunity is when the body’s immune system mistakenly attacks healthy tissue for unknown reasons.
Some reports in the medical literature state that pityriasis rosea affects females more often than males; others state that the disorder affects males and females in equal numbers. The disorder most commonly affects individuals between the ages of 10 and 35, but has been reported in all age groups including infants and the elderly. Pityriasis rosea occurs with greater frequency in the spring and autumn months.
A diagnosis of pityriasis rosea is made based upon identification of characteristic symptoms, a detailed patient history, and a thorough clinical evaluation. In the earlier stages of the disorder, additional tests such as blood tests or a biopsy may be necessary to distinguish pityriasis rosea from similar skin disorders.
The treatment is symptomatic and supportive. Many individuals may not require treatment and the rash usually clears up on its own within 1-3 months. Most treatment is geared to controlling or reducing itching. Such therapies include antihistamines, steroid creams or ointments,
A variety of therapies have been used to try to shorten the duration of the rash associated with pityriasis rosea. Such therapies include systemic corticosteroids, certain antiviral drugs such as acyclovir and famciclovir, and the antibiotic erythromycin. There is limited evidence to support any of these treatments.
Phototherapy is used for individuals with inflammatory skin disorders such as pityriasis rosea. Phototherapy may be administered by itself or in conjunction with topical treatments. Some affected individuals may be treated by greater exposure to sunlight.
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