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Chapter 24: Nephrotic Syndrome versus Nephritic Syndrome

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A 19-year-old African–American man is seen in your clinic. He reports over the past 2 weeks progressive swelling of his feet to the point it is difficult to wear shoes. He now also noticed his eye lids are puffy in the morning. He denies shortness of breath, abdominal swelling, chest pain, arthralgia, rash, or gross hematuria. He has had no significant past medical history. He takes no medications and denies illicit drug use. He reports his father and paternal uncle both had a history of kidney disease and needed dialysis but denies family history of malignancy.

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On physical examination, temperature is 37°C, blood pressure 142/85 mm Hg, pulse rate is 85 beats/min, and respiratory rate is 18 breaths/min. Cardiac and pulmonary examination is normal except for pitting edema to his knees. Abdominal examination is negative for hepatosplenomegaly and he has no flank tenderness.

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Laboratory studies:

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  • CBC: within normal values

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Renal function panel:

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Sodium 140
Potassium 3.8
Chloride 107
Bicarbonate 23
BUN 15
Creatinine 1.0
Albumin 2.5
Calcium 8.0
Phos 3.5
Spot urine protein: 456 mg/dL
Spot urine creatinine: 99 mg/dL
Urinalysis: 3+ protein; no erythrocytes or leukocytes noted

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Which of the following diagnostic tests is the most appropriate diagnostic test to perform?

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A. Antinuclear antibody and anti-dsDNA antibody assay

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B. Kidney biopsy

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C. Anti-phospholipase A2 receptor antibody assay

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D. Serum protein electrophoresis (SPEP)

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The answer is B. This patient’s clinical history, family history, and laboratory findings are very concerning for nephrotic syndrome related to focal segmental glomerulosclerosis and kidney biopsy is the only means by which this disease can be diagnosed.

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Antinuclear antibody and anti-dsDNA antibody assay would help to determine serologic evidence of systemic lupus erythematosus. Lupus nephritis is more commonly associated with a nephritic syndrome. Since this patient has severe proteinuria and no evidence of hematuria, his presentation is more consistent with nephrotic syndrome. Furthermore, positivity of ANA and anti-dsDNA does not always equate to lupus nephritis a kidney biopsy would need to be performed for a diagnosis.

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Antiphospholipase A2 receptor antibody assay is a test used in diagnosis and to monitor treatment response of primary membranous nephropathy. Though this patient’s presentation would be consistent with a membranous induced nephrotic syndrome, his age and being African–American makes FSGS more likely. Also, Antiphospholipase A2 receptor antibody is only present in approximately 70% of patient with primary membranous nephropathy, thus a kidney biopsy is still gold standard for diagnosis of membranous nephropathy.

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Serum protein electrophoresis (SPEP) is ...

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