A 17-year-old boy is evaluated in the office due to progressive facial puffiness, fatigue, and decreased appetite for the past month. Temperature is 36.7 C (98.1 F), blood pressure is 110/70 mm Hg, pulse is 80/min, and respirations are 18/min. Physical examination shows periorbital and pretibial edema. Serum laboratory results are as follows:
| Creatinine | 0.9 mg/dL |
| Albumin | 2.2 mg/dL |
Urinalysis shows 4+ proteinuria, no red blood cells, and no casts. A renal biopsy is performed. Immunofluorescence microscopy shows a diffuse, granular pattern of IgG and C3 along the capillary loops, and electron microscopy shows electron-dense immune deposits along the glomerular basement membrane, findings consistent with membranous nephropathy. Which of the following additional studies should be performed in this patient?
Membranous nephropathy | |
Epidemiology |
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Pathogenesis |
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Associated conditions |
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Presentation |
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Prognosis |
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BP = blood pressure; GFR = glomerular filtration rate; NSAIDs = nonsteroidal anti-inflammatory drugs. | |
This patient with edema and marked proteinuria has nephrotic syndrome from membranous nephropathy (MN), which is due to the accumulation of subepithelial immune deposits. Although MN is often idiopathic or primary (ie, autoantibodies against endogenous glomerular antigens) in adults, the diagnosis should prompt an evaluation for secondary causes, particularly in children who rarely develop primary disease (Choice E). The following conditions are associated with MN:
Because MN pathogenesis involves gradual podocyte damage from accumulating immune deposits, onset is typically subacute, unlike other common nephrotic syndromes that present acutely (eg, minimal change disease).
In patients with HBV, MN is caused by immune complexes formed from hepatitis B e antigen (HBeAg) and anti-HBeAg. Therefore, chronic HBV infection is a significant risk factor for MN, particularly in children. Evaluating all patients with MN with HBV serologies is recommended, although universal HBV vaccination had reduced the rates of HBV-associated MN.
(Choice A) Antistreptolysin O titers are useful in the diagnosis of poststreptococcal glomerulonephritis (PSGN). PSGN is commonly associated with hematuria, not seen in this patient. Although nephrotic-range proteinuria can occur, it is less common, and most patients have hypertension and elevated creatinine. Streptococcal infection is not associated with MN.
(Choice B) An audiology evaluation is indicated for patients diagnosed with Alport syndrome, which presents with hematuria due to defective type IV collagen. Patients often have a family history, and the disease classically presents following a respiratory tract infection. MN is not associated with increased risk of hearing loss.
(Choice C) Amyloidosis can present with nephrotic syndrome due to glomerular amyloid deposition. Echocardiography is indicated in these patients due to the risk of restrictive cardiomyopathy, which is not associated with MN.
Educational objective:
Membranous nephropathy causes gradual-onset nephrotic syndrome (ie, edema, proteinuria, hypoalbuminemia) and most commonly occurs in adults as primary disease. However, the diagnosis in any patient should prompt evaluation for a secondary cause, such as hepatitis B infection, autoimmune disease (eg, systemic lupus erythematosus), and malignancy.