Familial nephropathy in Bernese mountain dogs.

Between January 1988 and March 1992 nephropathies were frequently diagnosed in Bernese Mountain Dogs. During this period, 20 animals (16 females, four males), ages 2-5 years (average age at time of diagnosis = 3.3 years) presented with clinically renal insufficiency. Morphologic diagnosis of the renal lesions was identical in all cases, i.e., membranoproliferative glomerulonephritis (MPGN) with concomitant interstitial nephritis. Deposits of immunoglobulin-M (IgM) and of the third complement component were regularly demonstrated immunohistochemically in the glomeruli; deposits of immunoglobulin-A (IgA) and immunoglobulin-G (IgG) were found only in isolated cases. Reduplication of glomerular basement membranes, mesangial interposition, and subendothelial deposits of the immunocomplex type were also detected by electron microscopy. A pedigree analysis indicated that the MPGN in these 20 Bernese Mountain Dogs of approximately the same age was of hereditary genesis. Thus, MPGN should be allocated to the group of familial nephropathies. Serologically, high IgG titers against Borrelia burgdorferi were found in 17 dogs. These findings are discussed in relation to familial nephropathies in humans.