Fig. 1

Light and electron microscopic findings at first (a-d) and second biopsy (e-g). a, e Periodic acid–Schiff (PAS) staining at a low magnification (×100) in the first and second biopsy, respectively. Global or segmental sclerotic glomeruli (indicated by arrow) were increased at the second biopsy (e). Scale bars, 100 μm. b, c Segmental sclerotic glomerular images of Masson’s trichrome (b) and hematoxylin-eosin (HE) staining (c) at a high magnification (× 400). Granular swollen podocytes were indicated by arrowheads. Scale bars: 20 μm. d Electron microscopic views of podocytes filled with abnormal mitochondria were observed (indicated by arrowheads). Segmental foot process effacement of the epithelial cells was observed (lower left panel). Numerous dysmorphic mitochondria lacking cristae or with abnormally enlarged ones were observed in podocyte cell bodies (lower right panel). Scale bars: 5 μm. f Light microscopic views of the granular swollen podocytes (indicated by arrowheads) in the same focal segmental glomerulus under Masson’s trichrome (upper left panels), HE (upper right panels), PAS (lower left panels), and Periodic acid–methenamine-silver staining (lower right panels) (× 400). Scale bars: 20 μm. g Granular swollen podocytes (indicated by white arrowheads) were observed in sclerotic glomeruli (upper panels), but not normal-appearing glomeruli (lower panels) under Masson’s trichrome staining (× 400). Normal podocytes are indicated by black arrowheads. Scale bars: 20 μm. h Immunochemistry showing increased segmental staining of COX IV in glomeruli from this patient (left panel), but not in those from the control patient with no mitochondrial disease (right panel). COX IV-positive podocytes and normal podocytes are indicated by white and black arrowheads, respectively. Scale bars: 20 μm