An Unusual Kidney Lesion Presenting with Facial Edema, Hematuria, and AKI

Case Description

A 62-year-old White woman with a past medical history of hypertension and hypothyroidism presented with dyspnea on exertion. She reported a 3-week history of gross hematuria, facial swelling, and 10-pound weight gain. Laboratory examination showed the following: serum creatinine (sCr) 4.2 mg/dl (baseline sCr of 0.8 mg/dl), 24-hour urine protein 2.5 g/d, and serum albumin 3.7 g/dl. Urinalysis showed >500 mg/dL albumin, large urine blood, and >182 red blood cells. Urine microscopy revealed several acanthocytes but was devoid of casts. C3 was low at 35 mg/dl, Ch50 was low at 23, and antinuclear antibody was positive at 1:320 titer with a speckled pattern. Serum Ig free light chains revealed a free κ light chain of 77.0 mg/L (reference range 3.3–19.4 mg/L) and free λ light chains of 32.7 mg/L (reference range 5.7–26.3 mg/L), with a κ/λ ratio of 2.35 (reference range 0.26–1.65). Urine light chains were also obtained with urine free κ light chain of 209.74 mg/L (reference range 0.63–113.79 mg/L) and urine free λ light chains of 127.54 mg/L (reference range 0.47–11.77 mg/L), with a urine κ/λ ratio of 1.64 (reference range 1.03–31.76). Other autoimmune laboratory panels, including antineutrophil cytoplasmic antibody, anti-double-stranded DNA, and anti-glomerular basement membrane antibody, were negative.

Kidney biopsy was performed, and microscopic examination revealed glomeruli with global endocapillary and mesangial hypercellularity with obliterated capillary lumens and accentuated lobular configurations. The glomerular capillary walls were thickened, with prominent double contours (Figure 1A). Direct immunofluorescence revealed staining positive for κ light chains along the mesangial regions (Figure 1B), with λ light chains staining being negative. Electron microscopy showed numerous subendothelial and mesangial electron dense deposits (Figure 1C). Overall, the biopsy displayed evidence for membranoproliferative disease on immunofluorescence and electron microscopy with additional IgG3 κ subendothelial dense deposits. These findings are consistent with proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) (1).

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Figure 1.

Light microscopy, direct immunofluorescence, and electron microscopy from biopsy of the left kidney. (A) Glomerular capillary walls are thickened with prominent double contours. (B) Granular stains along capillary walls and in the mesangial regions for κ light chains with negative staining for λ light chains. (C) Numerous subendothelial and mesangial electron dense deposits with rare subepithelial electron dense deposits.

The patient required three sessions of nonemergent dialysis during the hospital admission and had significant kidney function improvement with initiation of high-dose glucocorticoids and rituximab. On follow-up in 3 months, repeat laboratory tests were performed, which showed a significant decrease in sCr to 1.3 mg/dl with a reciprocal increase in serum C3 to 82 mg/dl and Ch50 to >60 IU/ml. Positron emission tomography showed no suspicious fluorodeoxyglucose activity in the neck, chest, abdomen, or pelvis. Bone marrow aspiration and biopsy showed no definitive morphologic or immunophenotypic evidence of involvement of plasma cell neoplasm. Peripheral smear was also negative for plasma cell neoplasm.

Teaching Points

• Hematuria especially in the setting of AKI should be examined with microscopy to detect for signs of glomerular bleeding such as acanthocytes.

• The most common histologic pattern in PGNMID is global endocapillary and mesangial hypercellularity with obliterated capillary lumens and double contours of the glomerular capillary walls.

• The cause of PGNMID is typically IgG3k, even though this is the rarest of the IgG isotypes. IgG3 is nephritogenic and activates complement.

Disclosures

All authors have nothing to disclose.

Funding

None.

Author Contributions

T. Bond was responsible for conceptualization and wrote the original draft of the manuscript; C. Davis and A. Mims were responsible for visualization and reviewed and edited the manuscript.