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Archive: Teaching Points

Methotrexate-Induced Crystal Nephropathy

The patient is a 50-year-old male who presents with a creatinine of 4.2 mg/dL (baseline 1.0 mg/dL). He has been receiving high dose methotrexate for treatment of osteosarcoma. Image 1 shows a normal glomerulus. Image 2 shows moderate interstitial fibrosis. Image 3, 4, and 5 shows polarizable silver-positive crystals within the tubular lumens. This is a case of methotrexate-induced crystal nephropathy. Methotrexate-induced crystal nephropathy is characterized by acute tubular injury with scattered intratubular and interstitial needle-shaped, golden-brown crystals which are frequently arranged in annular structures. The crystals show birefringence under polarized light and are methenamine silver positive.  Methotrexate-induced crystal nephropathy...

BK Nephritis

The patient is a 45-year-old male with a past medical history significant for ESKD secondary to IgA nephropathy S/P renal transplant (3 years ago). He has been in his normal state of health but presented with an abnormal creatinine of 2.5 mg/dL on routine examination. His BK viral load was elevated at 25,000 copies in the serum. Figure 1 shows a normal glomerulus, figure 2 shows severe interstitial inflammation, figures 3 & 4 show marked tubulitis, and figure 5 shows a SV40 positive stain. This is a case of BK nephritis. BK virions are non-enveloped double-stranded DNA viruses. In immunohistochemistry,...

Type 1 Cryoglobulinemic Glomerulonephritis

The patient is a 75 year-old female who presents with proteinuria, a necrotic skin lesion on her lower extremity, and a creatinine of 5.5 mg/dL. Her serum complement levels (C3/C4) are low.  Serologies for ANA, dsDNA, rheumatoid factor, c-ANCA, p-ANCA, anti-GBM, and ASO are negative. Her cryoglobulins are positive. Image 1 shows hyaline thrombi and image 2 shows mild interstitial fibrosis. Images 3, 4, 5, and 6 are IgG, IgM, kappa, and lambda, respectively. This is a case of Type 1 cryoglobulinemia. Type 1 cryoglobulins are composed of a single monoclonal immunoglobulin that reversibly participates at low temperature (<37C).  Type...

Waldenström’s Macroglobulinemia

A 57-year-old white male presents with fatigue, mild proteinuria, and a creatinine of 1.5 mg/dL. He was diagnosed with lymphoplasmacytic lymphoma 6 months ago, but refused treatment. Figures 1 & 2 show prominent pseudothrombi and a membranoproliferative pattern of glomerular injury. Image 3 shows moderate interstitial fibrosis. Image 4, 5, 6, & 7 show IgG, IgM, kappa, and lambda, respectively. This is a case of cryoglobulinemic glomerulonephritis secondary to lymphoplasmacytic lymphoma (Waldenström's macroglobulinemia). Waldenström's macroglobulinemia is a rare B-cell lymphoma characterized by lymphoplasmacytic cell infiltration in the bone marrow and other organs and the presence of a monoclonal immunoglobulin M...

Light Chain Cast Nephropathy

A 75-year-old female is found to have a creatinine of 4.0 mg/dL on a routine laboratory examination. At the hospital, a CT scan shows lytic lesions within the skull. A SPEP shows an IgG kappa monoclonal protein. A bone marrow biopsy shows 5% plasma cells. A kidney biopsy is requested to look for monoclonal gammopathy of renal significance. Figure 1 shows a normal glomerulus. Figure 2 shows severe interstitial fibrosis. Figures 3 & 4 show abnormal, PAS negative "stiffened" casts with cellular reaction and fracture. Figures 5 & 6 show kappa and lambda immunofluorescence, respectively. This is a case of...

Membranous Nephropathy After Transplantation

The biopsy shows a recurrent membranous nephropathy within a transplant. Figure 1 shows "spikes" and "holes." Figure 2 shows mild interstitial fibrosis. Figures 3, 4, 5, and 6 shows IgG, kappa, lambda, and PLA2r, respectively. Figure 7 shows subepithelial and intramembranous deposits. Membranous nephropathy can arise in the graft from recurrence of the original disease, a de novo disease, and rarely as a donor-derived disease. Recurrence of the original disease can be seen as early as one week post transplant. Most cases of recurrent membranous nephropathy occur within the first few months following transplantation, whereas de novo membranous nephropathy usually...

Crescentic IgA nephropathy

The patient is a 17-year-old white female who presents with 2.85 grams/24 hr proteinuria, microscopic hematuria, and a creatinine of 3.2 mg/dl. She was in her normal state of health and was incidentally found to have abnormal lab values and urinalysis at a routine sport's physical. She reports that she had noticed a little more fatigue the last few months, but had blamed this on being busy at her job after school. Figure 1 shows focal fibrinoid necrosis. Figure 2 shows moderate tubular atrophy and interstitial fibrosis. Figures 3 & 4 show a segmental cellular crescent. Figure 5 shows several...

Scleroderma

The patient is a 32-year-old African American female who presents with hypertensive urgency, positive ANA, positive anti-RNA polymerase III antibody, schistocytes on the peripheral smear, forgetfulness, and a creatinine of 2. On physical examination, the skin is tight and thickened along the face ("masked face"), back, and proximal arms. Urinalysis shows 250 mg of proteinuria and no active urine sediment. Serologies for c-ANCA, p-ANCA, dsDNA, and anti-GBM are negative. The patient has scleroderma renal crisis. Figure 1 shows an ischemic glomerulus. Figure 2 shows moderate interstitial fibrosis. From low power, the intimal edema and intimal proliferation within the arteries is...

Cryoglobulinemic Glomerulonephritis

The patient is a 60-year-old male who presents with proteinuria, hematuria, and a creatinine of 2.8 mg/dL. He was in his normal state of health until 2 weeks ago when he noticed he was having trouble putting on his shoes. Serologies show low complements and an albumin of 2.3 g/dL. Serologies for ANA, c-ANCA, p-ANCA, hepatitis B, and hepatitis C are negative. No monoclonal spike is found on serum electrophoresis. Figure 1 shows accentuation of lobulation with both mesangial and endocapillary hypercellularity. This is a membranoproliferative pattern. Figure 2 shows a small, hyaline thrombus. Figure 3 shows moderate interstitial fibrosis....

VEGF Inhibitor

The patient is a 70-year-old white female who presents with 4 gm/24 hr proteinuria and a creatinine of 1.2 mg/dl. She has colon cancer with metastases to the liver, treated with chemotherapy and Avastin. The patient has recently had anemia, thrombocytopenia, ascites, and a urinary tract infection treated with nitrofurantoin. Her blood pressure has been under good control at 120/80. Figure 1 shows acellular closure of the capillary lumens and a "cotton-candy" appearance of the mesangium. Figures 2 and 3 shows capillary microaneurysms and segmental capillary hyalinosis. Figure 3 additionally shows double contours. Figure 4 shows moderate interstitial fibrosis. Figure...