Galactosialidosis is an autosomal recessive lysosomal disease associated with a deficiency of beta-galactosidase and neuraminidase. Described herein is the case of a young adult who had been diagnosed with galactosialidosis at 8 years of age. At the age of 30 years, proteinuria and hematuria appeared and the patient underwent a renal biopsy 1 year later. Light microscopy of the kidney sections indicated fine granular contents in the cytoplasm of glomerular endothelial and epithelial cells, arteriolar smooth muscles and proximal tubular epithelial cells on periodic acid silver-methenamin (PAM) stain. Electron microscopy of these cells indicated enlarged, smooth endoplasmic reticulum and lysosomes containing 150 nm-wide rods with a fine lattice structure at 66 A periodicity. Moreover, electron-dense deposits were located in the paramesangial area. Immunofluorescence staining indicated diffuse and global anti-human IgA and C3-positive staining as a mesangial pattern. Given these findings this patient was therefore diagnosed with both galactosialidosis and IgA nephropathy. This is the first report to describe light and electron microscopy observations of storage materials in the kidneys in young/adult galactosialidosis.