Pulsed intravenous methylprednisolone therapy for inflammatory myopathies: evaluation of the effect by comparing two consecutive biopsies from the same muscle.

To examine the effect of pulsed intravenous methylprednisolone (IVMP) on polymositis (PM) and dermatomyositis (DM), two biopsies were taken from the same muscle before and after IVMP in one case each of PM and DM. After IVMP, numerous muscle fibers were seen undergoing regeneration. Among all subsets of infiltrating cells that decreased in number, macrophages in the perivascular area decreased markedly. Also conspicuous was decrease of CD8+ cells in the endomysium in PM and that of B-cells in the perivascular area in DM. Among infiltrating cells, frequency of those which expressed the signal transducers and activators of transcription 1 (STAT-1) fell considerably, but remained still abnormally high. Regions on the endothelial cells of blood vessels that expressed MHC antigens and intercellular adhesion molecules 1 (ICAM-1) also decreased but remained more widespread than normal. These results agreed with the favorable clinical effect of IVMP, but showed that many of the immunological parameters remained abnormal.