A Clot and a Clue: When Pulmonary Embolism Leads to a Renal Diagnosis.

Primary membranous nephropathy (PMN) is one of the leading causes of nephrotic syndrome (NS) in non-diabetic adults, potentially progressing to end-stage renal disease. The detection of specific antibodies, such as anti-phospholipase A2 receptor (anti-PLA2R), is useful for diagnosis, risk stratification, and monitoring therapeutic response. Clinical presentation is usually insidious, with edema, malaise, fatigue, and anorexia, but may be complicated by NS complications as thrombotic events. We present the case of a 45-year-old man with bilateral pleuritic chest pain and hemoptoic cough for the past week, and peripheral edema over six months. Contrast-enhanced chest computed tomography (CT) revealed bilateral pulmonary embolism (PE). Laboratory tests highlighted hypoalbuminemia (2.4 g/dL), nephrotic-range proteinuria (12 g/24h) with preserved renal function, and positive anti-PLA2R antibodies (80 RU/mL). Secondary membranous nephropathy was excluded and renal biopsy was deferred. Treatment with rituximab was initiated, resulting in analytical improvement and disappearance of anti-PLA2R antibodies at six months. Close monitoring of renal function and early initiation of conservative treatment are essential to prevent disease progression and complications of NS, with immunosuppressive therapy potentially required in selected cases.