Overview
Definition
An acute, self-limiting papulosquamous eruption characterized by a primary 'herald patch' followed by a generalized secondary eruption in a 'Christmas tree' distribution.
Epidemiology
Most common in adolescents and young adults. Higher incidence in spring and autumn.
Etiology & Risk Factors
- Associated with reactivation of Human Herpesvirus 6 (HHV-6) or 7 (HHV-7)
Clinical Symptoms
- Herald Patch: Single, large (2-10 cm) salmon-colored oval plaque with a collarette of fine scale, typically on trunk
- Secondary Eruption (1-2 weeks later): Multiple smaller oval macules with scale, aligned along Langer's cleavage lines on the back ('Christmas tree' or 'fir tree' pattern)
- Mild to moderate pruritus
Clinical Approach
Diagnosis
- Clinical presentation
- Exclusion of secondary syphilis (RPR/VDRL) if palms/soles involved (Pityriasis rosea typically spares palms and soles)
Management
- Reassurance (self-limiting, resolves spontaneously within 6-8 weeks)
- Symptomatic: Topical emollients, mild topical steroids, or oral antihistamines for itching
- Acyclovir (may shorten duration if started early)
- Sunlight exposure
Complications
- Post-inflammatory pigmentary changes (especially in darker skin)