Abstract

A 51-year-old man with a past medical history of leukocytoclastic vasculitis presented to the dermatology clinic with a pruritic, erythematous rash of the bilateral lower extremities. The rash had come and gone in the same spots for the last 6 months. Examination revealed large pink, scaly thin plaques, some with an annular appearance, present on the bilateral lower extremities.  A shave biopsy was performed which revealed mounds of parakeratosis with underlying lymphohistiocytic perivascular inflammation and mild red blood cell extravasation. These findings are non-specific, but can be seen in pityriasis rosea (PR) and purpura annularis telangiectodes of Majocchi (PATM). Not only do these entities overlap histologically, they can also show clinical overlap too. PR classically presents with a herald patch on the trunk before disseminated lesions appear on the trunk and extremities. However, there is also an atypical PR that can have an unusual morphology and distribution of the lesions. PATM is a member of the pigmented purpuric dermatoses family that clinically presents as symmetrical, annular macules on the lower extremities. Differentiating these two benign lesions is clinically important because of the morbidity associated with PATM. PATM can be chronic, relapsing, and be difficult to treat. However, PR is a self-limited rash that tends to resolve on its own, without recurrence. After clinicopathologic correlation, a diagnosis of PATM was made over atypical PR. Herein, we present a case of PATM that is an important, rare entity to prevent misdiagnosis and improper and unnecessary treatment.