Physical Exam Findings in Pityriasis Rosea
Pityriasis rosea presents with a characteristic herald patch followed by a generalized eruption of oval, salmon-colored macules with peripheral collarette scaling distributed along Langer lines in a "Christmas tree" pattern on the trunk. 1, 2
Herald Patch (Primary Lesion)
- The herald patch appears first in approximately 80% of cases and is the most common presenting sign 1
- This lesion is larger and more noticeable than subsequent eruptions, typically measuring 2-5 cm in diameter 1
- It presents as an erythematous lesion with an elevated border and depressed center 2
- The herald patch has a delicate collarette of scales at the periphery 1
Secondary Eruption
- The generalized rash develops 4-14 days after the herald patch and continues erupting in crops over 12-21 days 1
- Individual lesions are 0.5-1 cm oval or elliptical macules 1
- Lesions appear dull pink or salmon-colored with a peripheral collarette of scales 1
- The distribution is bilateral and symmetrical, predominantly on the trunk and proximal extremities 1
Distribution Pattern
- The long axes of lesions orient along Langer lines (skin lines of cleavage) 1
- On the back, lesions create a characteristic "Christmas tree" pattern 1, 2
- On the upper chest, lesions may form a V-shaped pattern 1
- The rash primarily affects the trunk and proximal extremities 1
Atypical Presentations
- Approximately 20% of cases lack the herald patch, making diagnosis more challenging 1
- Inverse (flexural) pityriasis rosea presents with lesions concentrated in flexural areas rather than typical distribution 3
- Unilateral presentation can occur, affecting only one side of the body 4
- Atypical variants may require skin biopsy for definitive diagnosis 4, 3
Associated Symptoms
- Approximately 5% of patients experience a mild prodrome including headaches, fever, malaise, fatigue, anorexia, sore throat, enlarged lymph nodes, and arthralgia 1
- Pruritus may be present but is not universal 2
- The condition is self-limited with a typical course of 6-8 weeks 1, 2
Clinical Course and Management
- The disease is not contagious and does not require contact tracing or treatment of close contacts 5
- For typical cases, reassurance and symptomatic treatment with corticosteroids or antihistamines suffice 1, 2
- Acyclovir represents the best pharmacological option for extensive or persistent lesions, as it significantly improves rash resolution compared to placebo 6
- Oral steroids are most effective for itch resolution 6
- Pregnant women with pityriasis rosea require active intervention due to risk of spontaneous abortion 2