Diagnostic value of IgM deposition at the dermo-epidermal junction.

BACKGROUND: Granular immunoglobulin M (IgM) deposits at the dermo-epidermal junction (DEJ) are common in lupus erythematosus (LE); however, weak, interrupted, linear and granular patterns of IgM at the DEJ have been reported in sun-exposed skin in normal adults and in a heterogeneous group of diseases.

MATERIALS AND METHODS: We analyzed 200 patients with positive IgM direct tissue immunofluorescence deposition at the DEJ, alone or in combination with other immunoreactants, in order to determine the diagnostic significant of IgM deposition at the DEJ.

RESULTS: IgM deposition at the DEJ, commonly in combination with other immunoreactants, was associated with LE in 57.5% of patients. In cases with IgM deposition alone at the DEJ, only 12% had LE (strong intensities). IgM deposition at the DEJ was associated with other dermatoses in 42.5% of patients. In non-lupus patients, IgM deposition was the sole finding in 59% of cases, and was weaker and more focal than in LE patients.

CONCLUSIONS: IgM deposition at the DEJ in patients with LE tends to exhibit a strong intensity and is commonly detected in combination with other immunoreactants. IgM deposition alone at the DEJ, especially of weak intensity or focal in pattern, is noted in non-lupus patients, and has less diagnostic significance.