A case of systemic lupus erythematosus showing invagination of the podocyte into the glomerular basement membrane: an electron microscopic observation of a repeated-renal biopsy.

A case of systemic lupus erythematosus (SLE) showing invagination of glomerular epithelial cells into the glomerular basement membrane (GBM) has been reported. The patient was a 30-year-old woman who was diagnosed with SLE at the age of 25 and had been medicated with corticosteroid. At the age of 30, she was re-admitted into our hospital because of the relapse of lupus nephritis. Renal biopsy was performed twice: at the onset of SLE and the second admission. Morphologically, the results of the first and second renal biopsies were compatible with the classification of lupus nephritis class II. Immunofluorescent study revealed the mesangial deposition of IgG, IgA, C1q, C3 and membrane attack complex (MAC) in two renal biopsies. Especially, in the second renal biopsy, numerous vesicular structures composed of a unit membrane going into the epithelial site of the GBM were observed by electron microscopy (EM), but not in the first renal biopsy. Moreover, observations of serial sections of EM suggested that these vesicular structures were invaginated into the GBM and derived from a part of the podocytes.