Unilateral pityriasis rosea.

Sir,

Pityriasis rosea (PR) is an acute, self-limited disease, characterized by erythematous and squamous lesions and demonstrates minimal constitutional symptoms. Typical distribution of the lesions is the sudden onset of a squamous plaque, followed by a number of smaller, symmetrical squamous plaques, which are generalized on the trunk and proximal part of the extremities. Although PR usually occurs in a typical distribution and morphology, rarely, distinctive clinical and morphological variants may be observed. Still, unilateral PR is a very rarely encountered variant.[1]

A 20-year-old female presented with erythema over the left leg. Patient claimed that the redness started 10 days ago. Patient had no distinctive personal and family history. Dermatological examination revealed a well-demarcated squamous plaques with peripheral erythema over the proximal part of the left leg, some with a collarette of scale at the margin [Figure 1]. Histopathological evaluation of the biopsy specimen demonstrated hyperkeratosis, focal parakeratosis, irregular acanthosis, exocytosis, spongiosis, extravasated erythrocytes and perivascular mononuclear cell infiltration in dermis [Figure 2]. The total blood count, blood chemistry and erythrocyte sedimentation rate were within normal limits. KOH mount did not reveal any fungal elements. The patient was diagnosed as PR on clinical and histopathological evaluation. Since the patient had mild itching, topical methylprednisolone and oral antihistaminic were prescribed. Patient did not report any other problems during the follow-up and the lesions completely healed within the next 6 weeks.

Figure 1

Well demarcated, some with a collarette of scale at the margin, squamous plaques with peripheral erythema on the proximal part of the left leg

Figure 2

Hyperkeratosis, focal parakeratosis, irregular acanthosis, exocytosis, spongiosis, extravasated erythrocytes and perivascular mononuclear cell infiltration in dermis

Acute PR is a self-limited skin disease characterized by oval or round shaped, erythematous squamous plaques. It generally affects adolescents and young adults. Even though the etiopathogenesis is not clearly understood, possible causative factors are infectious agents, medications and environmental factors.[2] The diagnosis of PR based on careful history taking and physical examination. Atopic dermatitis, psoriasis, dermatophytosis, secondary syphilis, lichen planus, drug eruption and erythema annulare centrifugum are among the diseases that should be considered in the differential diagnosis.[3] The treatment is based on topical antipruritics and corticosteroids and ultraviolet light B phototherapy.[4]

Several clinical and morphological variants of PR have been reported in previous studies. Some of these variants include plaque, urticarial, vesicular, bullous, lichenoid type, non-palpable purpura, erythema multiforme-like lesions, gigantic plaque and exfoliative dermatitis.[5] To the best of our knowledge, only five cases with unilateral PR were reported previously.[12678] This report presents a rare, unilateral PR case with one-sided involvement.