Pityriasis Rosea: Clinical Features and Diagnosis
Pityriasis rosea is a common, acute, self-limiting papulosquamous skin disease primarily affecting children and young adults, characterized by a distinctive "herald patch" followed by oval erythematous squamous lesions along Langer's lines of cleavage on the trunk and proximal extremities. 1
Definition and Etiology
- Pityriasis rosea is associated with the endogenous systemic reactivation of human herpesvirus (HHV)-6 and HHV-7 1, 2
- The condition is self-limited, typically resolving within 6-8 weeks without treatment 1
- Peak incidence occurs during adolescence, primarily affecting individuals between 10-35 years of age 1
Clinical Presentation
Primary Features
- Herald patch: The most common presenting sign (80% of patients), appearing as a larger, more noticeable lesion than subsequent eruptions 1
- Secondary eruption: Develops approximately 4-14 days after the herald patch, continuing to erupt in crops over 12-21 days 1
- Typical lesions: 0.5-1 cm oval or elliptical, dull pink or salmon-colored macules with a delicate collarette of scales at the periphery 1
- Distribution pattern: Lesions follow skin lines of cleavage (Langer lines) 1
- "Christmas tree" pattern on the back
- V-shaped pattern on the upper chest 1
Prodromal Symptoms
- Mild prodrome occurs in approximately 5% of patients, including:
- Headaches, fever, malaise, fatigue
- Anorexia, sore throat
- Enlarged lymph nodes
- Arthralgia 1
Atypical Presentations
- Papular, purpuric, vesicular, follicular, erythema multiforme-like, and eczematous forms have been documented 3
- Localized and segmental variants may occur 3
- Herald patch may occasionally be the only cutaneous manifestation (abortive form) 2
- Diagnosis of atypical forms may require histopathological evaluation 3
Diagnostic Challenges
- Absence of the herald patch can make diagnosis challenging 1
- Multiple clinical variants may mimic other skin conditions 1, 3
- Histopathological examination may be required in atypical cases 3
Clinical Course and Duration
- Typical duration is 6-8 weeks 1
- Abortive forms (herald patch only) tend to have shorter duration and lower viral loads of HHV-6/7 2
- The condition is self-limiting in most cases 1
Differential Diagnosis
- Secondary syphilis
- Drug eruptions
- Tinea corporis
- Guttate psoriasis
- Nummular eczema 1
Management
- Reassurance and symptomatic treatment suffice for most cases 1
- Active intervention may be considered for:
- Severe or recurrent cases
- Pregnant women with the disease 1
- Treatment options include:
- Oral acyclovir (strongest evidence for shortening illness duration)
- Macrolides (particularly erythromycin)
- Ultraviolet phototherapy 1
Classification
- Modern classification systems consider both pathogenesis and clinical features rather than just morphological variations 4
- This approach helps identify atypical forms to avoid misdiagnosis and establish appropriate treatment 4