Discoid lupus erythematosus in a patient with myasthenia gravis.

Abstract

Dear Editor, A 49-year-old woman was referred to our department, complaining of erythematous lesions on the face that had appeared 6 months previously. A physical examination revealed a well-circumscribed, keratotic erythematous plaque on her left cheek (Fig. 1a). A few similar scaly erythemas were found on her forehead. She was suffering from myasthenia gravis (MG), which was confirmed by the detection of the acetylcholine receptor (AChR) antibodies in the serum and a typical electromyographic pattern. At the initial visit to us, she had been treated with oral prednisolone (10 mg/day). A thymectomy scar was also recognized (Fig. 1b). Laboratory data on blood chemistry including liver and renal function were within the normal ranges, but antinuclear antibodies (ANA) were detected in the serum (1 : 80, speckled). Histological examination showed inflammatory cell infiltration in the upper and mid-dermis. The epidermis showed irregular hyperkeratosis and slight liquefaction of the basal layer, and focal mononuclear cell infiltration in the dermis (Fig. 1c). Follicular plugging, liquefaction degeneration of basal cell layers, apoptotic cells scattered in the epidermis and interface cellular infiltrates were observed (Fig. 1d). Examination by direct immunofluorescence showed linear deposition of immunoglobulin M (IgM) in the epidermal basement membrane. The diagnosis of discoid lupus erythematosus (DLE) was made, and she was treated with topical corticosteroid cream, which had little effect. MG is an organ-specific autoimmune disorder closely associated with systemic lupus erythematosus (SLE).1 Recently, Castrejon et al.2 reviewed 16 patients with coexistence of SLE and MG, among whom 75% were female. Eight patients developed SLE after thymectomy, which may suggest that thymectomy plays a triggering role in the development of SLE, possibly by defective in T suppressor cell function. Alternatively, thymectomy may initiate the excessive production of autoantibodies in predisposed patients3 and result in the induction of SLE. By contrast, co-existence of MG and DLE is extremely rare in the literature and to our knowledge, this is the first report of such co-existence. The pathogenesis of DLE is likely to be multifactorial, and cellular and cytokine networks involving Th17 cells, type I interferon and tumor necrosis factor-α can be affected by environmental factors and genetic variations.4 Our case developed MG-associated thymoma, and DLE occurred 5 years after thymectomy. Although it is uncertain whether thymectomy induced DLE in our case, thymoma-derived autoreactive T-cells to the periphery are presumed to be a critical step in the development of thymoma-associated autoimmunity.5 This impaired immunity may have been relevant in the induction of DLE in the present case. Because hydroxychloroquine is not yet approved for LE in Japan, we applied topical corticosteroid cream to our patient. However, several cases have shown the beneficial effect of this drug for DLE,6 which may be expected in the treatment of DLE in the near future.