Pityriasis Rosea (cont.)

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How is pityriasis rosea diagnosed?

Pityriasis rosea is usually diagnosed by the skin appearance, particularly the onset of the distinct large herald patch and the symmetrical Christmas tree presentation. Also, the herald patch tends to have a unique, 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 after exposure to potassium hydroxide or "KOH" to detect fungus infection that could mimic pityriasis. Also, blood tests including rapid plasma reagent (RPR) may be done to detect secondary syphilis, which also may mimic pityriasis. In some cases, a skin biopsy may be required to detect fungus and other types of rashes.

What are some common misdiagnoses of pityriasis rosea?

The first herald patch of pityriasis rosea may look very similar in appearance to ringworm (tinea corporis). Pityriasis has also been mistaken with 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

  • psoriasis,
  • eczema,
  • fungal infection (tinea corporis),
  • secondary syphilis,
  • 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 lichenoides chronica,
  • parapsoriasis,
  • HIV-associated rash,
  • folliculitis.

What is the treatment for pityriasis rosea?

Most cases of pityriasis rosea require no treatment and resolve spontaneously. Treatment is not necessary if the rash does not cause symptoms. Typically, pityriasis will usually clear on its own in nine weeks without medical intervention or therapy.

The most common symptom is itching, which can be treated with topical steroid creams (like hydrocortisone cream) and oral antihistamines (like diphenhydramine [Benadryl], loratidine [Claritin], etc.). These will not shorten the duration of the rash but will decrease the itching. Another treatment for itching is UVB light or sunlight. However, exposure to sunlight increases the risk of skin cancer. Generally, the best treatment is to avoid being overheated by reducing exercise and avoiding hot showers and baths.

There has been some evidence of 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 for treatment.

Medically Reviewed by a Doctor on 8/29/2014

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