"Koko," a three-year-old female Labrador Retriever, presented to Cornell on August 26, 2002 with suspected Lyme glomerulonephritis. While Lyme disease in dogs typically presents as acute mono/ polyarthritis, atypical presentations of canine Lyme disease - including Lyme (glomerulo) nephritis

• are being recognized with increasing frequency. Lyme glomerulonephritis, more common in retriever breeds, is characterized by renal failure with protein-losing nephropathy. Histopathologic lesions consist of immune-mediated membranoproliferative glomerulonephritis, diffuse tubular necrosis, and interstitial inflammation; renal pathology is irreversible. "Koko's" history consisted of a transient single limb lameness, followed by worsening lethargy, anorexia, and polyuria. Laboratory tests revealed the presence of protein losing nephropathy and concurrent renal failure; a Lyme ELISA and Western blot were positive for antibody to infection. These results indicated glomerular injury, with Borrelia burgdorferi as a possible causative agent. Renal biopsies would be necessary to definitively diagnose the glomerulopathy, but "Koko's" thrombocytopenia and a prolonged BMBT represented contraindications for biopsy.