Value of dermoscopy in the diagnosis and prognostic evaluation of linear pigmented lichen planus.

We report the case of a 63-year-old woman who presented a 3-month history of hyperpigmented and pruritic skin lesions in the lumbar region. Physical examination revealed violaceous-brown macules in a linear distribution with an italic S morphology (Fig. 1). The nails and mucosas were not affected. The patient did not report using systemic or topical treatments, exposure to the sun, or trauma prior to the onset of the lesions. Dermoscopy revealed longitudinal pearly-white lines suggestive of Wickham striae (WS) and regressing brown macules in which there were grayish-brown dots and globules, some in a linear distribution following the outline of the WS or clustered in the depressed center of the WS (‘‘ashy holes’’) (Fig. 2). Skin biopsy revealed interface dermatitis with a lymphohistiocytic infiltrate, vacuolar degeneration of the basal layer, and apoptotic keratinocytes (Fig. 3). Based on the clinical, dermoscopic, and histologic findings, we made a diagnosis of pigmented linear lichen planus (LLP). A course of oral antihistamines and topical corticosteroids was prescribed, daily for the first month followed by an alternating regimen for 3 months. This produced a gradual resolution of the lesions, which left a residual postinflammatory hyperpigmentation. LLP is a condition of unknown etiology. It presents as hyperpigmented macules that usually arise in sun-exposed areas, but that are sometimes widespread.1 LLP differs clinically from classic lichen planus (LP) not only by the pigmentation, but also by its longer clinical course and the fact that the scalp, nails, and mucosas are not usually affected.1--5 One of the peculiarities of this case is the Blaschkoid distribution in an italic S shape. A review of the literature has revealed very few reports of LLP with isolated segmental manifestations, whether in a zosteriform distribution2 (in which case a history of herpes zoster must be sought, as this would suggest Wolf’s isotopic phenomenon3) or following the Blaschko lines,4,5 or with overlapping segmental manifestations,3 in which linear lesions are associated with widespread nonsegmental lesions, indicative of diseases with a polygenic inheritance, including LP and other common dermatoses, such as psoriasis.6 However, with the exception of our patient, all affected individuals have been of Middle Eastern or South American origin1--5; our patient is the first reported case of LLP in a Caucasian woman. The differential diagnosis is broad and includes linear dermatoses