Renal failure associated with mucopolysaccharidosis type I in a cat from a MPS I research colony

Renal failure was diagnosed in an 11-mo-old male domestic shorthair cat from a colony with mucopolysaccharidosis type I lysosomal storage disease. Grossly, the kidneys were enlarged and bulged on cut section. Histology revealed tubular necrosis and regeneration with severe interstitial macrophage accumulation. Tubular epithelial cells and interstitial macrophages were distended by abundant, large cytoplasmic vacuoles. Electron microscopy demonstrated severe tubular epithelial vacuolar degeneration with lysosomes distended by granular debris and mineral precipitates. Interstitial macrophages contained similarly distended lysosomes. Although the initial cause of the tubular injury was not identified, the presence of macrophages laden with storage product most likely exacerbated the disease. The macrophage infiltrate may have caused tubular ischemia by compressing peritubular capillaries and separating tubules from their blood supply. Because the kidney is not normally affected in MPS I, this case is an unusual presentation of a well-characterized disease. Furthermore, this report documents the diagnostic workflow used to investigate a single case of feline acute renal failure in the setting of numerous at-risk laboratory animals.