Introduction
Pityriasis rosea describes an acute, self-limiting rash which tends to affect young adults.
Epidemiology
- Incidence: 170.00 cases per 100,000 person-years
- Peak incidence: 20-30 years
- Sex ratio: more common in females 1:1
| Condition | Relative incidence |
|---|---|
| Pityriasis rosea | 1 |
| Guttate psoriasis | 0.03 |
| <1 | 1-5 | 6+ | 16+ | 30+ | 40+ | 50+ | 60+ | 70+ | 80+ |
Aetiology
The aetiology is not fully understood but is thought that herpes hominis virus 7 (HHV-7) may play a role.
Clinical features
Features
Examples of the hearld patch can be seen below:
The images below show the more widespread that follows:
- in the majority of patients there is no prodrome, but a minority may give a history of a recent viral infection
- herald patch (usually on trunk)
- followed by erythematous, oval, scaly patches which follow a characteristic distribution with the longitudinal diameters of the oval lesions running parallel to the line of Langer. This may produce a 'fir-tree' appearance
Examples of the hearld patch can be seen below:
The images below show the more widespread that follows:
Differential diagnosis
Differentiating guttate psoriasis and pityriasis rosea
| Guttate psoriasis | Pityriasis rosea | |
|---|---|---|
| Prodrome | Classically preceded by a streptococcal sore throat 2-4 weeks | Many patients report recent respiratory tract infections but this is not common in questions |
| Appearance | 'Tear drop', scaly papules on the trunk and limbs | Herald patch followed 1-2 weeks later by multiple erythematous, slightly raised oval lesions with a fine scale confined to the outer aspects of the lesions. May follow a characteristic distribution with the longitudinal diameters of the oval lesions running parallel to the line of Langer. This may produce a 'fir-tree' appearance |
| Treatment / natural history | Most cases resolve spontaneously within 2-3 months Topical agents as per psoriasis UVB phototherapy | Self-limiting, resolves after around 6 weeks |