Diagnostic Ambiguity of Encephalopathy in Advanced Kidney Disease: Multisystem Overlap in a Patient With Autosomal Dominant Polycystic Kidney Disease (ADPKD), Heart Failure, and Stiff Person Syndrome.

Altered mental status (AMS) in advanced chronic kidney disease (CKD) frequently reflects overlapping metabolic, cardiopulmonary, and neurologic contributors rather than a single unifying diagnosis. We present a 59-year-old woman with autosomal dominant polycystic kidney disease (ADPKD) progressing to end-stage renal disease (ESRD), congestive heart failure (CHF) with preserved ejection fraction (HFpEF), and stiff person syndrome (SPS) who developed recurrent encephalopathy accompanied by equivocal pulmonary findings and elevated cardiac troponin without electrocardiographic evidence of acute ischemia. Her hospital course was marked by severe renal dysfunction, metabolic acidosis, anemia, and intermittent electrolyte abnormalities. Management required iterative reassessment rather than reliance on a single explanatory diagnosis, included time-variable use of antibiotics and diuretics, continued chronic cardiometabolic therapies, and preparation for renal replacement therapy. This case highlights three practical teaching points: encephalopathy in ESRD is often multifactorial; troponin elevation in advanced kidney disease requires careful clinical correlation to avoid misclassification as acute coronary syndrome; and distinguishing pneumonia from pulmonary edema in volume-sensitive patients may necessitate repeated reassessment over time.