Chronic discoid lupus erythematosus: an immunopathological and electron microscopic study.
We studied 100 cases of chronic cutaneous discoid lupus erythematosus (DLE) to evaluate the diagnostic sensitivity of immunoreactant deposition and its possible role in basement membrane thickening. Histopathology was diagnostic in 71% of cases. Sixty-two percent (41/66) of lesions with thickened and 50% (17/34) with normal basement membrane had immunoreactant deposition. Ultrastructural study of 6 cases (3 with and 3 without immunoreactant deposition) with thickened basement membrane all showed reduplication of the lamina densa. Thickening of the basement membrane appears to be contributed mainly by reduplication of the lamina densa rather than by immunoreactant deposition. The direct immunofluorescence (DIF) test of lesional skin was positive in 58% of patients and was independent of duration of lesion, age and sex. Light microscopy has greater diagnostic sensitivity in confirming DLE lesions than DIF. Direct salt split skin technique did not increase DIF sensitivity. Scalp lesions showed the highest frequency (83%) of immunoreactant deposition. As C1q was the commonest immunoreactant found in our study, we suggest that it should be routinely used when DIF is employed in the evaluation of DLE. DIF is especially helpful in confirming cicatricial alopecia due to DLE.