Glomerular
lipidosis is a disease characterized by
lipid accumulation in mesangial cells but that has not been fully investigated in avian species. We examined four wild and two laboratory-reared Japanese rock ptarmigans (Lagopus mutus japonicus)--an endangered avian species--presenting vacuolar deposits in the glomeruli. All cases had vacuolar deposits in the glomeruli. In the wild cases, fewer than 30% of all glomeruli were affected, compared with more than 90% in the laboratory-reared cases. In the wild cases, most deposits were mild and restricted to the mesangial areas of glomeruli. In the laboratory-reared cases, nearly all of the deposits covered entire glomeruli. Electron microscopy of mild deposits revealed vacuoles in the cytoplasm of mesangial cells. These vacuoles were positive for
Sudan III,
Sudan black B,
oil red O,
Nile blue,
periodic acid-Schiff, Schultz test, and
digitonin stain and were negative for performaric
acid-Schiff stains. Based on these results, we diagnosed the glomerular lesion as glomerular
lipidosis caused by uptake of
low-density lipoprotein in mesangial cells. Except for one wild case, all cases exhibited renal tubular
oxalosis. The severity of tubular
oxalosis tended to be related to the severity of glomerular
lipidosis: In cases of mild glomerular
lipidosis, tubular
oxalosis was also mild or absent. We therefore diagnosed the primary lesion as glomerular
lipidosis accompanied by tubular
oxalosis. The four wild cases came from different zones and therefore had no opportunities to interbreed and no common relatives. We believe these data support the hypothesis that glomerular
lipidosis is a disease of the general population ofJapanese rock ptarmigans. This is the first report of glomerular
lipidosis accompanied by renal tubular
oxalosis in an avian species.