GLOMERULAR ULTRASTRUCTURAL FINDINGS SIMILAR TO HEREDITARY NEPHRITIS IN 4 ENGLISH COCKER-SPANIELS

Renal disease affecting 3 male and 1 female English Cocker Spaniels wa s studied. Clinical features of the disease included proteinuria and p rogressive deterioration of renal function. Dogs were 11 to 27 months old when euthanized because of severe chronic renal failure. Grossly, the renal cortices were thin. Light microscopic evaluation revealed di ffuse glomerular disease characterized by mesangial thickening, glomer ular fibrosis, periglomerular fibrosis, and glomerular obsolescence. B ased on these clinical and pathologic features, familial nephropathy o f English Cocker Spaniels was suspected despite the fact that the indi vidual dogs were not closely related. On transmission electron microsc opy. a distinctive ultrastructural lesion was observed the glomerular basement membranes (GBM) of all dogs. The GBM exhibited extensive thic kening, multilaminar splitting, and fragmentation. Electron dense depo sits, suggestive of immunocomplex glomerular disease, were notably abs ent. A similar ultrastructural GEM lesion is found in human beings and Samoyeds with hereditary nephritis, diseases caused by mutations in t he type IV collagen genes. Familial nephropathy in English Cocker Span iels may be a form of hereditary nephritis caused by a mutation in one of the collagen IV genes.