Pytiriasis Rosea

A self-limiting inflammatory skin disorder

Aetiology

• Exact cause unknown, but strongly linked to HHV-6/HHV-7

• Common in adolescents and young adults (ages 10–35)

• Not highly contagious

• Often preceded by mild prodromal symptoms (fever, malaise, sore throat)

Clinical presentation

Herald Patch

• First lesion in ~80% of cases

• Solitary, round or oval plaque

• Size: 2–10 cm

• Pink/salmon-colored with collarette of scale

• Often on the trunk

Secondary Eruption

• Occurs 1–2 weeks after herald patch

• Multiple oval, scaly lesions

• Distributed along Langer’s lines, forming a "Christmas tree" pattern

• Usually on trunk and proximal limbs

• Itching: mild to moderate (variable)

• Duration: typically 6–8 weeks, may persist up to 3 months

Atypical forms

• Inverse type (flexural areas)

• Vesicular, purpuric, or papular variants

• Pregnancy-associated cases require attention

Investigations

• Mainly clinical

• Herald patch + Christmas tree-like distribution is suggestive

• If uncertain:
• KOH test to rule out tinea corporis
• Serology for syphilis (RPR/VDRL) in atypical or palm/sole involvement
• Skin biopsy rarely needed

Management

• Antihistamines for itching

• Topical corticosteroids (low-mid potency)

• Moisturizers/emollients

• Avoid excessive heat or friction (may worsen itching)

• UVB phototherapy

• Acyclovir 400 mg 3x1 for 7 days