A 7-year-old boy is brought to the office due to swelling of the hands and feet. Two weeks ago, the patient was treated for anaphylaxis following a bee sting. During the past 10 days, he has had progressive hand and foot swelling, and his pants feel tighter than usual. The patient's urine has also become frothy. Examination shows periorbital edema and pitting edema of the hands and feet, as well as mild ascites. Lungs are clear to auscultation. Urinalysis results are as follows: Biopsy of this patient's kidneys would most likely show which of the following microscopy findings?

Question

A 7-year-old boy is brought to the office due to swelling of the hands and feet. Two weeks ago, the patient was treated for anaphylaxis following a bee sting. During the past 10 days, he has had progressive hand and foot swelling, and his pants feel tighter than usual. The patient's urine has also become frothy. Examination shows periorbital edema and pitting edema of the hands and feet, as well as mild ascites. Lungs are clear to auscultation. Urinalysis results are as follows:

Biopsy of this patient's kidneys would most likely show which of the following microscopy findings?

Quizplus · Accepted Answer

11ec160b_3a37_0c2d_9249_ffb1739b4753_MD0001_00 This pediatric patient developed nephrotic syndrome (ie, generalized edema, hyperlipidemia, hypoalbuminemia, massive proteinuria with resultant "frothy" urine) after a bee sting. This presentation suggests minimal change disease (MCD), the most common cause of nephrotic syndrome in young children. MCD is often idiopathic but can occur after an inciting event, including respiratory infections, immunizations, or insect sting/bite. Subsequent T-cell dysfunction leads to the production of a glomerular permeability factor (possibly IL-13) which damages podocytes and decreases the anionic properties of the glomerular basement membrane (GBM). Loss of negative charge results in the selective loss of albumin in the urine, which causes hypoalbuminemia and edema. Most children with MCD can be diagnosed presumptively based on clinical presentation, and renal biopsy is usually unnecessary. If biopsy is performed, light microscopy (LM) shows normal glomeruli, and no immunoglobulin or complement deposits are seen with immunofluorescent staining. However, electron microscopy (EM) shows diffuse podocyte foot process effacement and fusion. These abnormal findings are generally reversible after corticosteroid therapy, and most children experience rapid resolution with an excellent long-term prognosis. (Choice A) IgA nephropathy presents with nephritic syndrome; patients typically develop marked hematuria with red blood cell casts on urinalysis. Deposits of IgA are noted in the mesangium on EM and immunofluorescence microscopy (IF), whereas LM demonstrates resultant glomerular hypercellularity in affected segments. (Choice B) Poststreptococcal glomerulonephritis is a nephritic syndrome that typically occurs 2-4 weeks after infection with group A Streptococcus. LM demonstrates hypercellular glomeruli, whereas IF shows a "lumpy-bumpy" pattern of granular IgG and C3 deposition on the GBM. EM also demonstrates subepithelial immune complex deposits. (Choice C) Antiglomerular basement membrane disease causes a linear deposition of IgG and C3 on the GBM; it typically results in a crescentic glomerulonephritis (eg, nephritic syndrome; hematuria, red blood cell casts) visible on LM. EM demonstrates breakage of the GBM, but immune complex deposits are absent. (Choice D) Membranous nephropathy causes a nephrotic syndrome but is rarer in children; it is often associated with viral hepatitis, solid tumors, or lupus. LM reveals diffuse GBM thickening, which is due to the granular deposition of immune complexes (IgG and C3); EM demonstrates subepithelial deposits. Educational objective: Minimal change disease is the most common cause of nephrotic syndrome in children. Classic manifestations include proteinuria, hypoalbuminemia, and edema that are usually reversible with corticosteroids. The principal lesion is a diffuse foot process effacement that can be seen on electron microscopy. Light and immunofluorescence microscopy are normal.

A 7-Year-Old Boy Is Brought to the Office Due to Swelling