Drug eruption-like pityriasis rosea
Gilbert’s pityriasis rosea
Absence of initial single herald patch
Presence of initial single herald patch
Bright violet-red lesions
Salmon-pink lesions
Pruritus unrelieved by antihistamines
Pruritus relieved by antihistamines
Presence of increased eosinophils found in blood and skin infiltrate
Few eosinophils found in blood and skin infiltrate
Chronic course lasting 3–5 months
Acute course lasting 6–8 weeks
Fewer larger lesions with scaling involving the entire lesion
Many lesions diffusely on body with collarette of scaling
Oral lesions are more common
Oral lesions are rare
Post-inflammatory hyperpigmentation is a common sequela
Post-inflammatory hyperpigmentation is less commonly seen
More common in patients over age 35
More common in patients aged 10–35
Presentation and Characteristics
Primary Lesions
Pityriasis rosea-like drug eruption is a papulosquamous rash composed of bright violet-to-red macules, patches, and plaques with scaling across the entire lesion.
Secondary Lesions
Excoriations are commonly seen due to severe pruritus unrelieved by antihistamines. Effects of overtreatment with topical steroids can be seen due to the protracted course requiring a longer duration of treatment. These effects include skin atrophy and striae development, most commonly. Contact dermatitis may also develop.
Distribution
The macules, patches, and plaques appear mainly on the chest and trunk along the lines of cleavage in the skin. In many cases this creates a “Christmas tree” branching pattern.
Course
The bright violet-to-red macules, patches, and plaques will continue to appear for 3–5 months or until the inciting drug has been terminated.
Season
There is no seasonal preference as opposed to the idiopathic disease.
Age Group
The disease is more common in adults over 35.
Skin Biopsy
Histopathological examination will show acanthosis, focal parakeratosis, mild spongiosis with extravasation of red blood cells, and exocytosis of lymphocytes. A sparse to moderate superficial perivascular lymphohistiocytic infiltrate with many esosinophils can also be seen.
Differential Diagnosis
Idiopathic pityriasis rosea: Herald patch will be present; lesions occur mainly in young adults.
Psoriasis: Lesions have a silvery scale; commonly located on extremities, mainly the elbows and knees.
Lichen planus: Lesions are raised and occur commonly on mucous membranes.
Secondary Syphilis: The patient may report a history of genital lesions and may deny a history of pruritus. Syphilitic papules are infiltrative and have frequent involvement of the palms and soles with lymphadenopathy. A rapid plasma regain test would resolve doubts.
Tinea Veriscolor: Lesions are tan in color and irregularly bordered; lesions will form a dry adherent scale when scratched and fungi are seen on scraping.
Seborrheic dermatitis: The herald patch may be confused with a patch of seborrheic dermatitis, however seborrheic dermatitis lesions will appear as greasy, scaly lesions with a preference of distribution for the face, scalp, and genitalia.
Contact dermatitis: Eczematous features; commonly located on distal extremities in atopic individuals and those with occupational exposure to many chemicals.
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