The history should include questions about the following:
Close contacts with similar eruptions – This finding is uncommon because most cases of pityriasis rosea (PR) are sporadic
Medication intake – Several medications have been shown to cause a similar exanthema
Previous sexually transmitted disease, if appropriate
Possible pregnancy, if appropriate
Previous dermatologic disease and manifestations thereof, including previous PR
Recent upper respiratory tract infection (URTI)
The disease typically begins with a solitary patch, usually salmon-colored, that heralds the eruption and thus is commonly referred to as the herald patch or spot (see Physical Examination). This initial lesion enlarges over a few days to become a patch with a collarette of fine scale just inside the well-demarcated border. Dermoscopy evaluation using a triple-light source may be useful. 
Within the next 1-2 weeks, a generalized exanthem usually appears, although it may occur from hours to months after the herald patch. This secondary phase consists of bilateral and symmetric macules with a collarette scale oriented with their long axes along cleavage lines. This phase tends to resolve over the next 6 weeks, but variability is common and occasionally persistent. 
Pruritus is commonly evident in 25-75% of patients and usually of mild-to-moderate severity. Secondary eczematous changes can occur if pruritus is severe.
A small number (approximately 5%) of patients with PR have mild prodromal symptoms (eg, malaise, fatigue, headache, nausea, anorexia, chills, fever, and arthralgias) that precede the appearance of the herald patch. Lymphadenopathy may occur before the onset of the rash.
A classification dividing PR into classic, relapsing, persistent, pediatric, PR in pregnancy, and PR-like eruptions has been proposed. 
The typical initial skin lesion of PR, seen in more than 50% of patients, is a single 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, generally with a central wrinkled salmon-colored area and a dark red peripheral zone. This lesion, referred to as the herald patch or spot (see the image below), may develop anywhere on the body, including plantar skin, though it is most commonly located on the back. 
The herald patch usually shows a collarette of fine scales just inside its well-demarcated edges and may exhibit central clearing, much as in tinea corporis. This patch is something of a dermatologic enigma, in that it does not occur in any other known skin disease. The earliest stages of the patch may manifest as pink papules that can be mistaken for other lesions (eg, insect bites).
A generalized eruption then occurs, in which numerous lesions develop in crops over a period of 1-2 weeks (typically about 10 days) after the onset of the herald patch (though this eruption has also been known to occur as early as hours or as late as 3 months after the appearance of the patch). The eruption is symmetric and most commonly involves the thorax, back, abdomen, and adjoining areas of the neck and extremities; lesions are not usually observed on the face, hands, and feet.
These secondary lesions occur as macules and papules that are elliptical or ovular in shape and 0.5-1.5 cm across. Fine scaling and central wrinkling, with a cigarette paper aspect, is usually present. A characteristic feature is the collarette appearance of the scale, with edges peripherally attached and lifted up near the center of the lesion. However, unlike the scale in classic tinea corporis, the scale in PR does not extend to the border of the lesion.
The distribution of the lesions is usually bilateral and diffuse, with the long axes running parallel to skin tension lines. This produces the classic “Christmas tree” pattern on the trunk (see the image below). In children younger than 5 years, papular PR may be seen with a similar distribution. The rash can last as long as 6-8 weeks before fading.
With resolution of the eruption, postinflammatory pigment changes can be observed. Both hypopigmentation and hyperpigmentation can follow the rash. Individuals with dark skin are particularly likely to experience postinflammatory hyperpigmentation that may take a few months to heal.
Oral lesions of various types have been reported with PR, including punctate hemorrhages, ulcers (with or without raised borders), petechiae, papulovesicles, bullae, and erythematous plaques.  Most studies have found the incidence of these lesions to be lower than 10%; however, one study found it to be as high as 16%.
Variants and atypical forms
Approximately 20% of patients present with atypical or variant forms of PR. These variations may involve differences in the lesions themselves, differences in how they are distributed, or both.
Photosensitivity may occur. Photoexacerbated and photoprotected forms of PR have been documented, though photosensitivity is not a classic manifestation of the disease.
In 10-50% of cases, the herald patch may be absent, a finding that is more frequently observed in drug-induced PR. Alternatively, the herald patch may occur as multiple lesions or in atypical locations, such as the soles or the scalp. [35, 37] Sometimes, it is the only manifestation of the disease and is not followed by the typical rash.
An inverse pityriasis rosea may be seen, in which the generalized rash spreads to areas it usually does not affect, such as the face, hands, and feet. The face may be more commonly affected in young children, pregnant women, and black people. In such cases, the physician should consider secondary syphilis in the differential diagnosis, especially when involvement of the palms and soles is present.
Lesions may be localized to single areas, such as the abdomen, the groin, the axilla, the distal extremities, the palms, and the soles. A unilateral variant in which the lesions do not cross the midline has been described. 
A morphologic variant characterized by atypical large patches that tend to be fewer in number and coalescent has been described. In this variant, commonly referred to as pityriasis circinata et marginata of Vidal or limb-girdle PR, the eruption generally appears in the axillae, the groin, or both, with the trunk and extremities usually spared.  Individual patches are 3-6 cm in diameter, exhibiting the characteristic central clearing and collarette of scale with surrounding erythema.
The primary lesions may be papules, vesicles, pustules, or urticarial or purpuric plaques. [40, 41, 42] Papular PR tends to have scaling papules in the normal distribution; this form is believed to be more common in young children, pregnant women, and black people. Purpuric PR is seen in both adults and children and follows the usual presentation of the disease.  Erythema multiforme–like plaques may be evident.
Additional considerations in black patients
Black people are more likely to experience widespread forms of disease and concurrent lymphadenopathy, with hyperpigmentation upon resolution (48% of black children have residual hyperpigmentation  ). Black children are also more likely to have papular lesions (33%), scalp (8%) or facial (30%) involvement, and a shorter course of disease, with resolution sometimes coming within 2 weeks. 
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