Track

Case Reports

Abstract

A 39-year-old African American woman with a history of intermittent extremity rashes presented with a two-month history of a new pruritic eruption that spread centrifugally to include the right buttock, posterior thigh, and calf. Examination revealed unilateral, dark purple plaques with polygonal borders. Initial sections of a punch biopsy from the buttock revealed lichenoid inflammation with spongiosis involving the epidermis, initially favoring lichen planus. Deeper sections additionally revealed superficial to mid dermal perivascular and periadnexal lymphocytic infiltrate. Review of clinical photographs showed the eruption to follow a Blaschko-linear distribution. Clinicopathologic correlation supported the diagnosis of adult blaschkitis (AB), a rare inflammatory dermatosis. Blaschkolinear dermatoses comprise a spectrum of disorders that includes lichen striatus (LS) and AB, which differ by age predilection, clinical pattern, and histopathology. AB typically presents in adults (mean age 41) with pruritic, broad, multilinear bands - often truncal in distribution, with tendency to recur. LS, in contrast, primarily affects children, presents as asymptomatic, narrow, solitary bands on the limbs, and rarely recurs. Histologically, LS is classically lichenoid, whereas AB combines spongiosis with lichenoid interface dermatitis and dermal lymphocytic inflammation around adnexa and vessels. Both are self-limited, tending to resolve in weeks to months. Some authors have suggested that LS and AB are two endpoints on a spectrum known as Blaschkolinear acquired inflammatory skin eruption (BLAISE). The pathogenesis of AB remains uncertain, but proposed mechanisms include clonal expansion during embryogenesis and cutaneous antigenic mosaicism. Symptomatic management is typically with topical corticosteroids.