A case of unilateral linear lichen planus: related to orthopedic prosthesis or not?

Lichen planus (LP) is a skin disease characterized by violaceous, polygonal, flat-topped papules and plaques. The form with lichenoid papules in linear distribution is called linear lichen planus (LLP). It is usually distributed unilaterally and follows Blaschko lines. Lichen planus is seen in less than 0.2% of all LP patients [1]. To our knowledge, there has been no LPP case due to orthopedic implant reported in the literature before. We present a LLP patient because LLP is rarely seen and it might be precipitated by orthopedic endoprosthesis. A 64-year-old woman presented with a pruritic rash on her right leg. The patient had diabetes mellitus and bilateral blindness due to the diabetic retinopathy. She had undergone an operation because of a femoral bone fracture 1 year ago and an implant including chromium and cobalt was placed in this operation. The lesions appeared over the operation area 7 months after the operation. She was treated with topical steroids without any response. On physical examination she had violaceous and brownish papules that tend to form plaques in a linear distribution from the right hip to the knee (Figure 1). There were no mucosal involvement or nail changes. The histopathological examination revealed wedge-shaped hypergranulosis, destruction of the basal layer, band-like lymphocytic infiltration on dermoepidermal junction, melanin incontinence and melanophages on the upper-dermis (Figure 2). A diagnosis of LLP was made according to clinical and histopathological findings. We planned to perform a patch test but the patient refused. Treatment was initiated with a potent topical steroid. The patient did not come for follow-up. Linear lichen planus is a rare form of LP and represents less than 0.2% of all LP patients. Linear lichen pla-nus is different from linear configuration which is shorter and thinner of the LP due to the Koebner phenomenon. The differential diagnosis of LLP includes other der-matoses following the Blaschko lines such as the inflam-matory linear verrucous epidermal nevus, lichen striatus, linear lichen nitidus, linear lichenoid drug eruption, linear psoriasis, linear Darier's disease and linear graft-versus-host disease [1]. Histopathological examination provided definite diagnosis. The Blaschko lines are believed to trace the migration of embryonic cells. Some lesions of congenital and acquired skin diseases may follow the Blaschko lines. It is suggested that the acquired dermatoses following the Blaschko lines may occur because of viral infections or medications [2]. In our case we believe that the metal-containing orthopedic endoprosthesis may be the precipitating …