In the June issue of the American Journal of Kidney Diseases, Nasr et al report a variety of kidney biopsy findings in patients with multiple myeloma. This large retrospective study showcases the vast pathology seen in the kidney with paraproteinemias. The spectrum of kidney disease noted ranged from myeloma cast nephropathy to immunotactoid disease. The following questions will test your pathology knowledge of myeloma and the kidney.

1. A 68-year-old Caucasian man with a 14-year history of type II diabetes, hypertension, and chronic obstructive pulmonary disease has a κ light chain monoclonal spike in the serum that was interpreted as monoclonal gammopathy of undetermined significance. Over the last year, his serum creatinine rose from 1.4 mg/dL (eGFR, 50 mL/min/1.73 m²) to 8 mg/dL (eGFR, 7 mL/min/1.73 m²). The urinary sediment is bland, and a kidney biopsy is performed. What is the most likely diagnosis?

Left: H&E stain; original magnification, x40. Right: PAS stain; original magnification, x600. Images courtesy of Dr. Tibor Nadasdy.

A. Granulomatous interstitial nephritis with giant cells
B. Diabetic nephropathy with acute tubular necrosis
C. Myeloma cast nephropathy
D. Myoglobinuric acute kidney injury

2. A 69-year-old Caucasian woman presents to the emergency room with atrial fibrillation. She is found to have 3+ edema, ascites, and proteinuria quantified at 5 g/day. Serum creatinine is 1.2 mg/dL (eGFR, 45 mL/min/1.73 m²). Serologic workup indicates a positive ANA at 1:1280, and an IgG λ monoclonal spike is found in the serum with free λ light chains in the urine. A bone marrow biopsy shows slightly increased λ-restricted plasma cells, but no amyloid deposition. A fat pad biopsy is negative for amyloid. A kidney biopsy is performed. What is the most likely diagnosis?

Congo Red stain, right image under polarized light (original magnification, x200). Images courtesy of Dr. Tibor Nadasdy.

A. AL (light chain) amyloidosis
B. Monoclonal immunoglobulin deposition disease
C. Fibrillary glomerulonephritis
D. Mesangial proliferative (ISN/RPS Class II) lupus nephritis

3. A 72-year-old Caucasian man with a 10-year history of well-controlled type II diabetes and hypertension presents with nephrotic syndrome (8.4 g/day proteinuria) and microscopic hematuria.  His blood pressure is well-controlled at 128/76 mm Hg, and his BMI is high at 40. He does not have retinopathy. Serologic testing is negative, but he is found to have a small IgG κ monoclonal spike in the serum and monoclonal κ light chains in the urine. Serum creatinine is 3.0 mg/dL with an eGFR of 21 mL/min/1.73 m².  A kidney biopsy is done. What is the most likely diagnosis?

Top: PAS stain; original magnification, x400. Bottom: EM; original magnification, x20,000. Images courtesy of Dr. Tibor Nadasdy.

A. Nodular diabetic glomerulosclerosis
B. Monoclonal immunoglobulin (κ light chain) deposition disease
C. Amyloidosis
D. Dense deposit disease

4. A 64-year-old Caucasian man with a history of hypertension is found to have a κ light chain monoclonal spike in both the serum and urine. He reports no history of diabetes. A 24-hour urine collection reveals 2.8 g proteinuria of which 1.8 g is free κ light chain. Serum creatinine is 1.5 mg/dL (eGFR, 47 mL/min/1.73 m²). Urinalysis reveals glucosuria. A bone marrow biopsy shows few atypical κ-restricted plasma cells. A kidney biopsy is performed. What is the most likely diagnosis?

EM; original magnification, x5000. Image courtesy of Dr. Tibor Nadasdy.

A. Myeloma cast nephropathy
B. Toxic tubulopathy with abnormal mitochondria
C. Fabry disease
D. Proximal tubulopathy secondary to intracytoplasmic monoclonal κ crystal formation

Here’s to a fruitful learning experience!

Post prepared by Tibor Nadasdy, MD, Director of Renal and Transplant Pathology, The Ohio State University, and AJKD Kidney Biopsy Teaching Case Advisory Board Member; and Kenar Jhaveri, MD, eAJKD Blog Editor

To see the answers, please click here.

To view the article abstract or full-text (subscription required), please visit AJKD.org.