Isomorphic skin reaction with DNCB in SLE and DLE.

DNCB sensitization was studied in 76 cases of systemic and 44 of discoid lupus erythematosus and in 101 immunosuppressed and tumor patients as controls, as well as in 40 contact-sensitized eczematous and 115 unselected patients. Sensitization of patients with discoid LE and that of mixed patients are of the same order, while it is lower in the systemic LE group. The highest incidence was found in the polysensitized positive control group; the lowest in the immunosuppressed and tumor patients. DNCB sensitization showed clear age dependency in the different groups. At the site of the DNCB exposure, isomorphic reactions were found in 43% of discoid and 25% of systemic LE patients. Histological and immunofluorescence studies supported the findings of the clinical picture, i. e. the appearance of isomorphic reactions at the site of the exposure cannot be related either to the intensity of the early reaction or with the developing intensity.