Current Issue

Spring/Summer 2025, Vol. 32 No. 1

Hong Kong J. Dermatol. Venereol. (2025) 32, 88

Answers to Dermato-venereological Quiz

HF Cheng 鄭學輝

Differential diagnosis to truncal papulosquamous eruptions includes psoriasis, pityriasis lichenoides chronica, subacute eczema, cutaneous eruption of secondary syphilis, tinea corporis, tinea versicolor, erythema annulare centrifugum, drug eruption, and pityriasis rosea.
Skin scraping for mycology study, diagnostic skin biopsy for histopathology.
Acanthosis with foci of spongiosis. Hyperkeratosis with foci of parakeratotic mounds and hypogranulosis. Superficial peri-vascular lymphocytic infiltration, extravasated erythrocytes, and homogenised papillary dermal collagen.
The final diagnosis was Pityriasis rosea. A Herald patch was seen over his right upper chest, which is the largest in terms of size. Typically, Herald patch is a forerunner and will persist throughout the entire clinical course. The clinical condition will improve gradually. With time all cutaneous lesions will clear up without scarring. Clinical lesions of Pityriasis Rosea would typically last for one to three months. After that, spontaneous resolution is usually the rule rather than exception. Pityriasis Rosea may be associated with HHV-6 or HHV-7 viral infection. Symptomatic treatment with topical steroid may be required if pruritus is troublesome. The role of short course oral acyclovir is still controversial. A couple of systematic reviews and meta-analysis had showed that it may help with symptomatic control. It is prudent to exclude secondary syphilis or drug eruption as their morphology overlaps and distinction based on clinical criteria alone may be difficult. Pityriasis Rosea per se is not infectious. Contact precaution is not required as the carers will not acquire this skin condition via daily acquaintances. Explanation and reassurance to the patients and their carer are all that is required.