A102-02 Podocyte Under Pressure: Collapsing Lupus Podocytopathy Diagnosed When Kidney Biopsy Beat the Marrow Call

Introduction Collapsing focal segmental glomerulosclerosis (FSGS) is an uncommon but aggressive histologic variant of lupus nephritis (LN) that may present as lupus podocytopathy, does not always match to International Society of Nephrology/Renal Pathology Society (ISN/RPS) Class I-V criteria. These lesions indicate severe injury to podocytes followed by a rapid deterioration of the kidney function. The prognosis is especially unfavorable in the case of advanced chronic histologic damage, which indicates the importance of early biopsy and treatment in suspected cases. Case Presentation A 60-year-old previous healthy male presented with nausea, vomiting, and hemoptysis after travel to Jamaica. Initial laboratory studies revealed severe acute kidney injury (creatinine 39.1 mg/dL, BUN 200 mg/dL), hyperkalemia (8.0 mmol/L), and oliguria requiring ICU admission for emergent hemodialysis. Urinalysis revealed nephrotic-range proteinuria (urine protein-to-creatinine ratio 7.3 g/g; albumin-to-creatinine ratio 3,062 mg/g). Complements were low (C4 <8 mg/dL; C3: 67 mg/dL). ANA >1:1280 (speckled), anti-U1 RNP and anti-Ro markedly elevated; other autoimmune antibodies were negative. Serum and urine protein electrophoresis revealed an IgG kappa monoclonal spike (0.96 g/dL) with mildly elevated Kappa/Lambda ratio (2.46). With no high paraprotein burden or amyloid deposition, monoclonal gammopathy of undetermined significance (MGUS) was considered more likely rather than monoclonal gammopathy of renal significance (MGRS). Given high suspicion for immune-mediated nephropathy, pulse-dose IV methylprednisolone (1 g/day × 3) was initiated. Kidney biopsy (Day 8) showed collapsing FSGS with mesangial immune complex deposits, ∼80% tubular atrophy/interstitial fibrosis, arteriosclerosis and globally sclerosed glomeruli (See Below). Findings were consistent with collapsing lupus podocytopath. Nephrology and rheumatology were consulted and renal recovery was deemed unlikely. The patient was discharged on prednisone taper and outpatient hemodialysis. Discussion Lupus podocytopathy with collapsing FSGS is a rare, aggressive, and characterized by podocytes proliferation and capillary tuft collapse. It may progress rapidly to kidney failure despite immunosuppressive therapy. Unlike classic lupus nephritis, lupus podocytopathy may show only minimal or mesangial immune deposits and does not comply with Class I to V patterns of ISN/RPS. An early kidney biopsy is essential since extensive tubules atrophy or interstitial fibrosis (>50%) is correlated with poor prognosis. The co-occurrence of monoclonal proteinemia should be considered as indicative of additional workup of MGRS as potentially resembling immune-mediated glomerulopathies. In this case, the histologic and serologic findings favored autoimmunity-associated podocytopathy rather than paraprotein-related injury. This highlights the importance of timely biopsy and coordinated, multidisciplinary assessment in patients with severe, unexplained AKI and nephrotic-range proteinuria.