Lupus, the Great Mimicker: Unmasked by Urine Microscopy

Introduction: Systemic Lupus Erythematosus (SLE) can present in a variety of ways, making it difficult to diagnose. By analyzing the urine microscopy of a critically ill patient, a complex case of SLE was identified and effectively treated. Case Description: A 75 year old female with a history of chronic L staghorn calculus, recurrent pyelonephritis, and L kidney atrophy presented with dizziness and difficulty ambulating and was found to have multifocal strokes. She developed acute hypoxic respiratory failure with bilateral infiltrates, thought to be multifocal pneumonia. ICU team noted bloody endotracheal secretions. Nephrology was consulted for acute kidney injury (AKI). Serum creatinine: 1.5-2.0mg/dL (baseline 0.9-1.0 mg/dL). Urinalysis showed persistent hematuria, long attributed to staghorn calculus, with new proteinuria. Urine microscopy revealed RBC casts, acanthocytes, and oval fat bodies seen in figure 1. Serologies revealed ANA >1:1280, elevated dsDNA, anti-smith, RNP, SSA Ro antibodies, low C3/C4, but otherwise negative. Urine protein creatinine ratio: 2.42mg/mg. Given the urine sediment, nephrology recommended bronchoalveolar lavage, revealing diffuse alveolar hemorrhage. Biopsy was deferred given her acute illness and solitary kidney, but data was strong enough to presume class III/V or IV/V lupus nephritis as well as pulmonary and CNS lupus vasculitis. She promptly received a steroid pulse and cyclophosphamide. She was ultimately extubated, had complete resolution of her AKI, had less active urine sediment, and is making a neurologic recovery. Discussion: The novelty of our case includes the simultaneous presentation of three severe manifestations of SLE, but more importantly highlights the pivotal role of urine microscopy in the evaluation of AKI with an “active” UA. Although not a replacement for biopsy, urine microscopy allowed for prompt treatment, multi-disciplinary agreement, and identification of the unifying diagnosis, lupus vasculitis.A. RBC cast B. Oval fat body C. folded RBC cast with embedded acanthocyte D. mixed cellular, predominant RBC cast