Publish date: Posted on
Last updated: May 31, 2022
Keywords #
pityriasis rosea
inflammatory dermatosis
Diagnosis #
Pityriasis rosea (PR) is an inflammatory dermatosis presenting with red patches and fine overlying scale. The disease is characterized by a prominent 2-5 cm primary patch, known as the herald patch, followed 1 to 20 days later by similar, smaller, oval salmon-pink patches.1 In most cases, these patches are located primarily on the chest and back and follow lines of cleavage, in what has been described as a “Christmas tree” distribution.[1] Atypical cases of the disease also exist, in which size, distribution, or morphology of lesions may vary.[2] The disease is self-resolving and typically clears within 6 to 12 weeks without complication.
Key Concepts #
- PR is characterized by a herald patch followed by similar, smaller, oval salmon-pink patches with a trailing collarette of scale.
- Patch distribution follow lines of cleavage (Langer’s lines). Truncal predominance is typical but atypical (or inverse) patterns may involve extremities.
- There is a possible correlation or association with reactivation of herpesviruses 6 and 7.
- The rash is often idiopathic but can be drug-related.
- The rash is self-limited and generally resolves within 6-12 weeks.
Epidemiology #
[1] PR is relatively common with 0.5 to 2% of the population affected at some point in their lives. The condition most often affects teenagers and young adults, but it can affect people of any age. There is no gender predominance.
Clinical Features #
- PR typically presents with a characteristic 2-5 cm, oval, salmon-pink, scaly patch or plaque, called the herald patch.
- This is followed 1 to 20 days later by similar, smaller, oval pink patches or plaques on the trunk that follow Langer’s lines of cleavage.
- The rash may be itchy but is often asymptomatic and resolves with in 6 to 12 weeks.
- Postinflammatory pigmentary changes are common.
- Atypical presentations may change these clinical features. A wide variety of atypical morphologies are possible, including papules, vesicles, urticarial plaques, purpura, and targetoid lesions.
- Rash may also present in unusual patterns (inverse, acral) or with much larger or confluent lesions.
- Prolonged or recurrent disease courses are possible but rare.[2]
Differential Diagnoses #
- Tinea (tinea corporis, tinea capitis, tinea cruris, tinea pedis, barbae)
- Tinea versicolor
- Cutaneous T-cell lymphoma
- Subacute cutaneous lupus erythematosus
- Guttate psoriasis
- Nummular dermatitis
- Drug eruptions
Diagnostic Workup #
PR is typically a clinical diagnosis but may be supported by biopsy showing spongiosis and mild lymphocytic perivascular infiltrates on histopathology.[1] Eosinophils are typical of drug-induced PR.[1]
Proposed clinical diagnostic criteria:[3]
- Major clinical features
- Discrete circular or oval lesions
- Scaling on most lesions
- Trailing peripheral collarette of scale with central clearance on >2 lesions
- Minor clinical features
- Truncal and proximal limb distribution (<10% of lesions distal to mid-upper arm and mid-thigh)
- Most lesions along skin cleavage lines
- Herald patch arrival greater than or equal to 2 days before other lesions
Treatment #
In general, PR does not need to be treated aggressively as the lesions will resolve on their own. However, a gentle skin care routine such as, bathing with plain water and unscented soap, moisturizing dry skin, and avoiding excess sun exposure may be beneficial. Oral acyclovir may help clear the skin eruption more rapidly. Topical steroid creams or ointments may be used to reduce itch while waiting for the rash to clear. In severe or persistent cases, phototherapy may be considered.[4]
References #
- Nair, Pragya A., and Steve S. Bhimji. “Pityriasis Rosea.” StatPearls [Internet]. StatPearls Publishing, 2018.
- Mahajan, Khushbu, et al. “Pityriasis rosea: An update on etiopathogenesis and management of difficult aspects.” Indian journal of dermatology 61.4 (2016): 375.
- Zawar, Vijay, and Antonio Chuh. “Applicability of proposed diagnostic criteria of pityriasis rosea: Results of a prospective case-control study in India.” Indian journal of dermatology 58.6 (2013): 439.
- Villalon-Gomez, Jose M. “Pityriasis Rosea: Diagnosis and Treatment.” American family physician 97.1 (2018).
