Pityriasis rosea is an acute, self-limiting skin eruption with a distinctive and constant course. The initial lesion is a primary plaque followed after 1 or 2 weeks by a generalized secondary rash with a typical distribution and lasting for about 6 weeks. In the literal sense, Pityriasis rosea means benign pink scale.
Pityriasis rosea accounts for 2% of skin related outpatient visits. The disease favors the hot, dry season.
Pityriasis rosea is most common in ages 10-35 years but can occur in all age groups.
It is more common in females than in males.
It is found more in people living in close groups, like families, students, and military personnel.
A higher incidence of pityriasis rosea is also noted among patients with decreased immunity, for example, bone marrow transplant recipients.
Ampicillin is known to increase the distribution of the eruption.
Pathophysiology of Pityriasis Rosea
Pityriasis rosea has often been considered to be of viral origin. It is often linked to upper respiratory tract infections and thought to be a viral eruption.
But the search for an infectious agent has been unsuccessful.
Eruptions similar to pityriasis rosea has been noted with many drugs. These are difficult to differentiate.
- Acetylsalicylic acid
- BCG vaccine
- Human papillomavirus vaccine
- Anti-tumor necrosis factor agents
The disease typically begins with a salmon-colored patch called the herald patch or spot. This initial lesion enlarges over a few days to become a patch with a rim of fine-scale just inside the well-demarcated border. Prodromal symptoms like malaise, fatigue, headache, chills, fever, and arthralgias may precede herald patch in some patients.
Following this, generalized eruption usually appears within 1-2 weeks but the duration could vary from a few hours to months.
The rash is bilateral and symmetric and oriented with its long axis along cleavage lines. Different crops of rashes may erupt and heal at different times. The rash is itchy and secondary eczematous changes can occur if itching is severe.
A history of any previous exposure or medicine intake that might cause eruptions may be present.
On examination, herald patch is a pink macule or patch, which gradually expands over a few days to become an oval or round plaque that is 2-10 cm in diameter, with a central wrinkled salmon-colored area and a dark red peripheral zone.
It may develop anywhere on the body, including plantar skin, though it is most commonly located on the back. The earliest stages of the patch may manifest as pink papules.
This kind of patch does not occur in any other known skin disease.
Secondary eruption is symmetric and most commonly involves the thorax, back, abdomen, and adjoining areas of the neck and limbs. These lesions are generally not observed on the face, hands, and feet.
The lesions have fine scaling and central wrinkling. The collar-like appearance of the scale is unique with edges peripherally attached and lifted up near the center of the lesion.
The distribution of the lesions is usually bilateral and diffuse along the skin tension lines producing a Christmas tree pattern on the trunk.
With the resolution of the eruption, hypopigmentation or hyperpigmentation can occur.
Individuals with dark skin are particularly likely to experience postinflammatory hyperpigmentation that may take a few months to heal.
Oral lesions are found in 10-15% of patients and are seen as
- Punctate hemorrhages
- Erythematous plaques.
Almost one-fifth of the patients do not have the typical presentation.
- Photosensitivity may be present.
- Herald patch may be absent in 10-50% of cases, generally with drug-induced pityriasis rosea. Herald patch may occur as multiple lesions or in atypical locations, such as the scalp. Sometimes, herald patch is not followed by an eruption.
- In inverse pityriasis rosea, the rash spreads to areas which are usually not affected, such as the face, hands, and feet.
- Lesions may be localized to single areas, such as the abdomen, the groin, the axilla, the distal extremities, the palms, and the soles.
- Atypically large patches that are less in number have been described.
- Scaling papules are more common in young children and pregnant women.
- In black people, the disease is more likely to be widespread. Concurrent lymphadenopathy occurs and hyperpigmentation is more likely. Black children are also more likely to have papular lesions, scalp or facial involvement. They also have a shorter course of the disease.
Following differentials should be considered
- Drug Eruptions
- Erythema Annulare Centrifugum
- Erythema Dyschromicum Perstans
- Erythema Multiforme
- Guttate Psoriasis
- Kaposi Sarcoma
- Lichen Planus
- Nummular Dermatitis
- Pediatric Syphilis
- Pityriasis Lichenoides
- Pityriasis Rubra Pilaris
- Seborrheic Dermatitis
- Tinea Corporis
- Tinea Versicolor
The diagnosis of pityriasis rosea is made clinically in most cases. Lab tests are not necessary but the following tests can be done to rule out other causes of eruptions.
- Complete blood count
- ESR may be elevated
- Serum protein level, globulin level, and albumin level – Usually normal but may show mild increase.
- Rheumatoid factor
- Cold agglutinins, and cryoglobulins levels
- KOH test of herald patch may be done to check tinea corporis
- Because pityriasis rosea can be confused with secondary syphilis, a rapid plasma reagin or Venereal Disease Research Laboratory (VDRL) test should be performed to rule out syphilis.
- HIV test should also be considered in these patients.
Treatment of Pityriasis Rosea
Pityriasis rosea is a self-limiting disease and the treatment is supportive. In most cases, it is not necessary to treat. Following measures should be taken
- The patient should avoid irritants like harsh soaps, hot water, tight clothing, and scratching.
- Topical zinc oxide, calamine lotion, emollients, and oral antihistamines are useful for itching. If the rash is severe, topical steroids can be applied.
- Ultraviolet radiation therapy – rapidly relieves the itching.
- Topical antifungals in cases where tinea infection is a concern or possibility
Pityriasis rosea is a self-limiting, generally benign disorder for which the prognosis is excellent.
Pigmentary changes, which develop as lesions heal, occur, especially in black people.
Atopy, seborrheic dermatitis, and acne vulgaris are more common in patients with pityriasis rosea than in controls.
Pityriasis rosea during pregnancy may cause premature delivery and fetal death, especially when it develops within the first 15 weeks of gestation.