Christmas tree rash, or pityriasis rosea, is an acute, self-limiting, papulosquamous eruption with a duration of 6-8 weeks.
- Human herpesvirus 6 (HHV6) or human herpesvirus 7 (HHV7)
URTI precedes all other symptoms (69% cases)
- Single, 2-10-cm oval red “herald” patch
- Appears on abdomen (classically) or in ‘hidden’ positions (in the armpit, for example)
- May also appear as a cluster of smaller oval spots, and be mistaken for acne (D/D)
- 7–14 days after the herald patch,
- Many small (5–10 mm) patches of pink/red, flaky, oval-shaped rash appear on the torso.
- “Christmas-tree” distribution
- Spread widely across the chest first, following the rib-line
- Small, circular patches may appear on the back and neck several days later.
A patient is diagnosed as having pityriasis rosea if:
- On at least 1 occasion/clinical encounter, he/she has all essential + atleast 1 optional clinical features
- On all occasions/clinical encounters related to rash, he/she does not have any of the exclusional clinical features.
The essential clinical features are the following:
- Discrete circular or oval lesions,
- Scaling on most lesions, and
- Peripheral collarette scaling with central clearance on at least 2 lesions.
The optional clinical features are the following:
- Truncal and proximal limb distribution, (< 10% of lesions distal to mid-upper-arm and mid-thigh),
- Orientation of most lesions along skin cleavage lines, and
- A herald patch (not necessarily the largest) appearing at least 2 days before eruption of other lesions, from history of the patient or from clinical observation.
The exclusional clinical features are the following:
- Multiple small vesicles at the centre of two or more lesions,
- ≥ 2 lesions on palmar/plantar skin surfaces, and
- Clinical/serological evidence of secondary syphilis.
Condition usually resolves on its own, and treatment is not required.
- Help the lesions disappear faster if started during the first week of eruption
- Lotions, oral antihistamines, and/or topical glucocorticoids