Pityriasis Rosea

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Introduction

Pityriasis rosea is a common, mild, inflammatory exanthem. It tends to be seasonal, more common during the fall, winter and spring in temperate countries.

In some West African countries, it is more common during the early part of the rainy season (though cases are seen throughout the year). It is common among siblings or other family/household members.

The seasonal clustering and household
concurrence are suggestive of an infective origin.

Increasingly regarded as a delayed reaction to a viral infection (most likely Human Herpes Virus 7).

Symptoms and clinical features pityriasis rosea

  1. Largely a disease of adolescents and in young adults, but it has been described all age groups
  2. Rarely, there is an observable prodrome of pharyngitis, malaise and mild headache
  3. The initial lesion in 20-80% of cases (“herald patch”) is often larger than the later lesions and precedes the general eruption by 1 – 30 days
    • Often found on the trunk, but may appear on the face or extremities
    • Oval with a collarette of scales
    • May be diagnosed as “ringworm” before the other lesions appear
  4. Other lesions consist of multiple erythematous macules progressing to small, red papules on the trunk
  5. Sun-exposed areas are spared
  6. Papules enlarge and become oval with long axes parallel to each other, and following lines of cleavage: the so-called “Christmas tree” pattern
  7. Pruritus is mild or absent
  8. Some lesions may be atypical: vesicular, crusted, purpuric, follicular, lichenoid, and psoriasiform A variant, inverse pityriasis rosea also occurs
    • Believed to be commoner in blacks
    • Affects the face, neck, distal extremities and the flexures
  9. Use of ampicillin early in the course of the eruption causes an explosive exacerbation of eruptions which become more inflammatory and urticarial
    • Lesions may become impetiginized
  10. The disease persists for about 6 weeks but may last for 3-4months
  11. Healing may occur with post inflammatory hyper/hypopigmentation
  12. Recurrences are uncommon (about 1%) but the lesions are usually mild and localized.

Differential diagnoses

  • Secondary syphilis
  • Exanthematic or pityriasis rosea-like drug eruptions
  • Lichen planus
  • Guttate psoriasis
  • Tinea corporis
  • Tinea versicolor
  • Seborrhoeic dermatitis
  • Viral exanthems
  • Pityriasis lichenoides chronica

Complications of pityriasis rosea

  • None

Investigations

Non-specific

VDRL

  • If secondary syphilis is suspected (e.g. lesions on palms and soles with/without lymphadenopathy)

Treatment for pityriasis rosea

Treatment objectives

  1. To relieve symptoms (if any)
  2. Reassure patients about the harmless, self limiting nature of the eruption

Drug treatment

Topical:

  • Urea cream.
  • Useful as a hydrating agent: apply twice daily

Systemic:

Oral antihistamine

  • If pruritus is bothersome (see Urticaria)

Systemic corticosteroids:

If complicated by ampicillin exanthematic eruption

  • Triamcinolone acetonide 40 mg intramuscularly as a single dose

Antibiotics:

If lesions are impetiginized

  • Erythromycin 500 mg orally every 6 hours for 14 days

Notable adverse drug reactions, caution

  • Antihistamine;
  • Triamcinolone: see Urticaria

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