A 32-year-old man complains of recurrent hematuria since his youth. The hematuria typically occurs following upper respiratory tract infections. Vital signs are normal. Urinalysis shows proteinuria, hematuria, and a few red blood cell casts. Laboratory studies disclose normal levels of BUN and creatinine. The ANA and ANCA tests are negative. For the patient, which of the following patterns of IgA immunofluorescence would be expected in the renal biopsy?

**Core Concept**
The patient's presentation suggests an immune-mediated glomerulonephritis, specifically IgA nephropathy (Berger's disease), characterized by the deposition of IgA antibodies in the glomeruli, often in response to an upper respiratory tract infection.

**Why the Correct Answer is Right**
IgA nephropathy is a common cause of recurrent hematuria, particularly following upper respiratory tract infections. The disease is characterized by the deposition of IgA antibodies in the glomeruli, which can lead to inflammation and damage to the glomerular capillaries. The presence of IgA deposits can be identified through immunofluorescence studies on a renal biopsy sample. In IgA nephropathy, the IgA deposits typically show a mesangial and capillary wall staining pattern, which is a hallmark of the disease.

**Why Each Wrong Option is Incorrect**

* **Option A:** This option is incorrect because IgA nephropathy is not typically associated with the deposition of IgG or C3 in the glomeruli.
* **Option B:** This option is incorrect because membranous nephropathy is a different disease entity characterized by the deposition of IgG and C3 in the subepithelial space.
* **Option C:** This option is incorrect because membranoproliferative glomerulonephritis is a different disease entity characterized by the deposition of C3 and IgG in the mesangium and capillary walls.

**Clinical Pearl / High-Yield Fact**
IgA nephropathy is often referred to as the "most common cause of recurrent hematuria worldwide." The disease can progress to end-stage renal disease in a small percentage of cases, particularly in patients with persistent proteinuria or hypertension.

**Correct Answer:** D.

✓ Correct Answer: C. Mesangial deposition