Background Lupus erythematosus tumidus (LET) is a rare disease which was first described in 1909 but has not always been considered as a separate entity of cutaneous lupus erythematosus (CLE) in the international literature. Objectives To compare characteristic features of different subtypes of CLE and to analyse whether LET can be distinguished as a separate entity in the classification system of the disease. Methods The study involved 44 patients with CLE, including 24 patients with LET, 12 with discoid lupus erythematosus (DLE) and eight with subacute CLE (SCLE), from two centres in Germany. A core set questionnaire and an SPSS database were designed to enable a consistent statistical analysis. Results Location of skin lesions did not differ significantly between the CLE subtypes; however, the activity score was significantly lower in LET than in DLE (P < 0.01), and the damage score was significantly lower in LET than in SCLE (P < 0.01) and DLE (P < 0.01). Photosensitivity and antinuclear antibodies were confirmed to be different in LET compared with SCLE and DLE but without statistical significance. Moreover, histological analysis of skin biopsy specimens showed that abundant mucin deposition is significantly more present in LET compared with SCLE (P < 0.01) and DLE (P < 0.01) while prominent interface dermatitis and alteration of hair follicles were absent in LET. Conclusions Several significant differences were found between LET and other subtypes of CLE with regard to clinical, histological and laboratory parameters. These data strongly indicate that LET should be defined as a separate entity in the classification of CLE.

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These data characterize the CLASI as an overall useful instrument to analyse disease activity and damage in CLE. However, the CLASI does not give an accurate assessment of all disease subtypes; therefore, a revision of the CLASI with critical analysis of all parameters is recommended.