[Cutaneous paraneoplastic syndrome as an immunologic phenomenon exemplified by paraneoplastic subacute cutaneous lupus erythematosus].

Two case reports and a review of the literature on paraneoplastic figurate erythemas with lupus erythematosus (LE)-specific histolopathology illustrate cutaneous paraneoplasia as an immunological phenomenon. Subacute cutaneous lupus erythematosus (SCLE) is characterized by photosensitive, annular or papulosquamous skin lesions with LE-specific histopathology in association with circulating anti-SS-A (Ro) auto-antibodies. The SS-A (Ro) antigen is a complex of cytoplasmic ribonucleoproteins that translocate to the surface of keratinocytes under UV irradiation. Sequestered cytosolic antigen that is expressed on the cell surface is presented to T lymphocytes by professional antigen presenting cells in the context of specific MHC class II molecules. The initiation of the specific immune response, the expansion of antigen-specific T helper cells, and the differentiation of B cells to antibody producing plasma cells depend on the further interaction with antigen. The risk of a self-perpetuating autoimmune response relies on further release of auto-antigen. It is conceivable that in paraneoplastic SCLE tumor antigen with homology to SS-A (Ro) leads to photosensitive autoreactivity. The review of the literature reveals 9 other cases of SCLE associated with internal malignancy. The most common associated tumors were bronchial and mammary carcinoma. The latency between the appearance of skin lesions and the diagnosis of an underlying tumor was between one month and three years (mean: 10 months). In all cases, skin lesions improved with cancer therapy, in three cases they (re)appeared in association with relapse of tumor.