A 4 year-old boy, develops a large erythematous rash around the site of a mosquito bite. One month later, he is taken to a pediatrician because of a puffy face and swollen ankles. The scanty urine sample has a reddish-brown hue, and contains both red blood cells and protein. Which of the following distinctive features would be most likely to be seen on renal biopsy?

The disease is poststreptococcal glomerulonephritis, which can follow either streptococcal pharyngitis (one to two weeks after the infection) or skin infection (three to six weeks after the infection). The child is showing signs of both nephritis (hematuria) and nephrosis (puffy face and swollen ankles). The characteristic feature of this disease on renal biopsy is the presence of subepithelial humps, visible either by light or electron microscopy. Fusion of podocyte foot processes suggests minimal change disease. IgA in the mesangium suggests Berger's disease. Linear IgG deposits suggests anti-glomerular basement membrane disease, which is called Goodpasture's disease if it is accompanied by pulmonary damage. Onion-skinning of renal aerioles suggests malignant hypeension.