Vesicular pityriasis rosea

Differential diagnosis

The differential diagnosis includes tinea corporis, secondary syphilis, guttate psoriasis, and autoimmune bullous diseases.¹

Tinea corporis, a skin infection primarily caused by dermatophyte fungi, typically presents as a red circular rash with a slightly raised border and a clearer center, resembling a ring.⁴ There may be scaling or vesicles at the edges, and the lesions can be itchy or mildly irritated. The rash is usually localized in the infected area but can spread over time if not treated. A positive fungal microscopy examination is fundamental for diagnosis. In our patient, fungal microscopy examination was negative, ruling out tinea coproris.

Secondary syphilis diagnosis requires an etiologic examination. However, syphilis can be difficult to diagnose due to its diverse manifestations. The presence of nonpruritic red or reddish-brown papulosquamous eruptions on any part of the body, including the palms and soles, along with the presence of plasma cells on histopathologic examination, is indicative of secondary syphilis.⁵ Negative results on fluorescent treponemal antibody absorption testing ruled out secondary syphilis in our patient.

Guttate psoriasis is a relatively rare variant of psoriasis characterized by an abrupt onset of small, diffuse, salmon-colored papulosquamous papules with silver scales.⁵ Tiny points of blood are visible when the scales are rubbed or picked off. Guttate psoriasis exhibits a predilection for children and youth and is frequently associated with streptococcal infections. It has characteristic histologic features of psoriasis, including mild epidermal hyperplasia, focal spongiosis, disappearance of the granular layer, and migration of neutrophils into the epidermis to produce epidermal or subcorneal collections.^5,6 Histopathologic examination in our patient revealed no evidence of guttate psoriasis or an acantholytic process.

Autoimmune bullous diseases such as pemphigus, bullous pemphigoid, and dermatitis herpetiformis are a group of rare skin disorders characterized by widespread erythema and blisters. They occur due to autoantibodies disrupting the junction between the dermis and epidermis.⁷ Diagnosis of these disorders involves comprehensive evaluations, including clinical features, histologic examination, and immunohistologic assessment. In our patient, autoimmune diseases were ruled out based on a normal result on antinuclear antibody testing, the absence of associated symptoms, and negative direct immunofluorescence studies of the biopsy sample.