VA Boston Medical Forum

A Veteran Presenting With Leg Swelling, Dyspnea, and Proteinuria

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Case Presentation. A 63-year-old male with well-controlled HIV (CD4 count 757, undetectable viral load), epilepsy, and hypertension presented to the VA Boston Healthcare System (VABHS) emergency department with 1 week of bilateral leg swelling and exertional shortness of breath. He reported having no fever, cough, chest pain, pain with inspiration and orthopnea. There was no personal or family history of pulmonary embolism. He reported weight gain but was unable to quantify how much. He also reported flare up of chronic knee pain, without swelling for which he had taken up to 4 tablets of naproxen daily for several weeks. His physical examination was notable for a heart rate of 105 beats per minute and bilateral pitting edema to his knees. Laboratory testing revealed a creatinine level of 2.5 mg/dL, which was increased from a baseline of 1.0 mg/dL (Table 1), and a urine protein-to-creatinine ratio of 7.8 mg/mg (Table 2). A renal ultrasound showed normal-sized kidneys without hydronephrosis or obstructing renal calculi. The patient was admitted for further workup of his dyspnea and acute kidney injury.

Jonathan Li, MD, Chief Medical Resident, VABHS and Beth Israel Deaconess Medical Center (BIDMC). Dr. William, based on the degree of proteinuria and edema, a diagnosis of nephrotic syndrome was made. How is nephrotic syndrome defined, and how is it distinguished from glomerulonephritis?

Jeffrey William, MD, Nephrologist, BIDMC, Assistant Professor of Medicine, Harvard Medical School. The pathophysiology of nephrotic disease and glomerulonephritis are quite distinct, resulting in symptoms and systemic manifestations that only slightly overlap. Glomerulonephritis is characterized by inflammation of the endothelial cells of the trilayered glomerular capillary, with a resulting active urine sediment with red blood cells, white blood cells, and casts. Nephrotic syndrome mostly affects the visceral epithelial cells of the glomerular capillary, commonly referred to as podocytes, and hence, the urine sediment in nephrotic disease is often inactive. Patients with nephrotic syndrome have nephrotic-range proteinuria (excretion of > 3.5 g per 24 h or a spot urine protein-creatinine ratio > 3.5 g in the steady state) and both hypoalbuminemia (< 3 g/dL) and peripheral edema. Lipiduria and hyperlipidemia are common findings in nephrotic syndrome but are not required for a clinical diagnosis.1 In contrast, glomerulonephritis is defined by a constellation of findings that include renal insufficiency (often indicated by an elevation in blood urea nitrogen and creatinine), hypertension, hematuria, and subnephrotic range proteinuria. In practice, patients may fulfill criteria of both nephrotic and nephritic syndromes, but the preponderance of clinical evidence often points one way or the other. In this case, nephrotic syndrome was diagnosed based on the urine protein-to-creatinine ratio of 7.8 mg/mg, hypoalbuminemia, and edema.

Dr. Li. What would be your first-line workup for evaluation of the etiology of this patient’s nephrotic syndrome?

Dr. William. Rather than memorizing a list of etiologies of nephrotic syndrome, it is essential to consider the pathophysiology of heavy proteinuria. Though the glomerular filtration barrier is extremely complex and defects in any component can cause proteinuria, disruption of the podocyte is often involved. Common disease processes that chiefly target the podocyte include minimal change disease, primary focal and segmental glomerulosclerosis (FSGS), and membranous nephropathy, all by differing mechanisms. Minimal change disease and idiopathic/primary FSGS are increasingly thought to be at differing points on a spectrum of the same disease.2 Secondary FSGS, on the other hand, is a progressive disease, commonly resulting from longstanding hypertension, diabetes mellitus, and obesity in adults. Membranous nephropathy can also be either primary or secondary. Primary membranous nephropathy is chiefly caused by a circulating IgG4 antibody to the podocyte membrane antigen PLA2R (M-type phospholipase A2 receptor), whereas secondary membranous nephropathy can be caused by a variety of systemic etiologies, including autoimmune disease (eg, systemic lupus erythematosus), certain malignancies, chronic infections (eg, hepatitis B and C), and many medications, including nonsteroidal anti-inflammatory drugs (NSAIDs).3-5 Paraprotein deposition diseases can also cause glomerular damage leading to nephrotic-range proteinuria.

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