ObjectiveTo review what is known and highlight knowledge gaps regardingLyme nephritis (LN).Data SourcesPublications identified via PubMed using the keywords “Borrelia burgdorferi,” “Borreliosis,” “glomerulonephritis,” “protein‐losing nephropathy,” “autoimmunity,” and “retriever,” and as generated by investigators working in the fields ofBorreliosis and immune‐mediated glomerulonephritis.Human Data SynthesisPostborrelial immune‐mediated glomerulonephritis was described recently in 6 people; 3 responded to antimicrobials/steroids, 1 to antimicrobials/angiotensin‐converting enzyme inhibitor/warfarin, 1 required hemodialysis but became hemodialysis independent after 5 months and treatment with antimicrobials, steroids, plasmapheresis, immunoglobulin, and 1 did not respond to steroids and angiotensin‐converting enzyme inhibitor and still requires hemodialysis.Veterinary Data SynthesisLyme nephritis is seen in <1–2% ofLyme seropositive dogs, with an average onset at 5–6 years. Labrador and Golden Retrievers are predisposed to this condition. Prior or concurrent lameness is described in 9–28% cases. Historical presentations include acute progressive protein‐losing nephropathy with membranoproliferative glomerulonephritis, tubular necrosis/regeneration, and interstitial nephritis, but possibly milder forms exist. Complications include thromboembolic events, hypertension, effusive disease, and oliguric/anuric renal failure. Diagnostic tests help stage disease and rule out other causes. Renal biopsy is advocated early, when intervention may help, and to prove if immune‐complex disease exists. Treatment includes standard therapy for protein‐losing nephropathy, long‐term antimicrobials, and perhaps immunosuppressive therapy.ConclusionsThere is no experimental model ofLNto study predisposing factors, pathogenesis, onset, progression, treatment, or prevention. There are no predictive tests to identify the few individuals at highest risk, therefore all seropositive dogs should be screened and monitored for proteinuria.Lyme nephritis mimics other forms of protein‐losing nephropathy and sometimesLeptospirosis. Renal biopsy helps show if immune‐complex disease exists, but may not proveLNspecifically. More studies are warranted on dogs withLyme‐specific immune‐complex deposition to evaluate risk factors, understand pathogenesis, variability of expression, and to validate treatment and prevention protocols.