Which is the most accurate diagnosis? A 40-year-old woman presents to her physician with complaints of blood in her urine and decreased urine output for the past week. She had a sore throat 3 weeks ago, which has since resolved. Her temperature is 37° C (98.6° F), heart rate is 70/min, and blood pressure is 147/93 mm Hg. Physical examination reveals bilateral pedal edema to the mid-calf. In addition to several serologic tests, the patient undergoes renal biopsy.

Rapidly progressive glomerulonephritis

The correct answer is F. The image shows a crescent of epithelial cells and fibrin as well as a hypercellular glomerulus, which together are characteristic of rapidly progressive glomerulonephritis (RPGN). Furthermore, the clinical scenario demonstrates a nephritic syndrome, with hematuria, oliguria, and hypertension, which one would expect with RPGN. In about 50% of cases, RPGN is caused by deposition of immune complexes, but it can also be caused by pauci-immune glomerulonephritis and antiglomerular basement membrane (GBM) disease (called Goodpastures syndrome when associated with pulmonary hemorrhage) Answer A is incorrect. The most common cause of end-stage renal disease in the United States is diabetic nephropathy, which causes a nephrotic syndrome. A renal biopsy would show KimmelstielWilson lesions, which are nodules of mesangial matrix Answer B is incorrect. Patients with Goodpastures syndrome present with pulmonary hemorrhage and glomerulonephritis. The syndrome is caused by anti-GBM antibodies. On immunofluorescence, renal biopsy would show a linear pattern tracing the basement membrane of the glomeruli. Anti-GBM antibodies are implicated in the pathogenesis of type 1 RPGN Answer C is incorrect. IgA nephropathy, or Bergers disease, often presents in children as hematuria following infection. Renal biopsy shows mesangial expansion due to deposition of IgA Answer D is incorrect. Lupus nephritis is the most serious symptom of systemic lupus erythematosus and often determines the prognosis of the disease. Additional symptoms of systemic lupus erythematosus included malar rash, discoid rash, photosensitivity, oral ulcers, arthritis, serositis, neurologic disorders, and immunologic disorders. Lupus nephritis causes a nephrotic syndrome with proteinuria, hypoalbuminemia, edema, and hyperlipidemia; many patients also develop hypertension. Renal biopsy is important to determine treatment, and histologic findings are classified in five patterns, including mesangial and subendothelial deposits (called wire-loop lesions) Answer E is incorrect. Poststreptococcal glomerulonephritis is a common cause of nephritic syndrome that occurs about 10 days after pharyngitis. On light microscopy one would see diffuse proliferative glomerulonephritis without crescents. Electron microscopy would show subepithelial humps. Most cases are subclinical, and usually patients recover on their own, but some go on to develop RPGN, like the patient in this vignette Answer G is incorrect. Renal amyloidosis is associated with chronic inflammatory diseases and causes nephrotic syndrome. Glomerular amyloid deposits can be seen on renal biopsy by staining with Congo red and examining the specimen under polarized light.