BRCU 2025: Test Your Knowledge
A 64-year-old woman presents to you for evaluation of CKD. One year ago, her serum creatinine level was 0.9 mg/dL and, upon presentation, is 2.1 mg/dL. She has a medical history of hypertension, coronary artery disease, osteoarthritis, and obesity. She feels well and has no symptoms.
Her current medications are irbesartan, carvedilol, hydrochlorothiazide, aspirin, and, occasionally, ibuprofen.
On exam, her blood pressure is 126/84 mm Hg, heart rate is 60 bpm. She is obese without lower extremity edema. Laboratory tests return the following values: Na 138 mEq/L; K 4.2 mEq/L; Cl 107 mEq/L; HCO3 22 mEq/L; BUN 36 mg/dL, Cr 2.1 U/L; glucose 84 mg/dL; total protein 6.1 g/dL; and albumin 3.9 g/dL. Her lung function tests are normal.
A CBC count reveals WBC 4.8/μL, Hgb 10.7 g/dL, HCT 31.2%, and platelets 223,000/μL.
UA results are as follows: pH 6.0, protein 2+, blood negative, UAC 720 mg/g, and urine protein to creatinine ratio 1.1 g/g. No cells or casts found on microscopy.
The patient's HIV test, hepatitis studies, and ANA, complement, and phospholipase A2 receptor values are all negative or normal. Serum and urine immunofixation are without monoclonal proteins.
Renal ultrasound reveals normal-sized kidneys and an increase in echogenicity bilaterally. A renal biopsy specimen under light microscopy reveals mesangial expansion and hypercellularity. There are no spikes, holes, or crescents. Congo red stain is negative. IF microscopy reveals smudgy 2+ mesangial staining of IgG, C3, and co-equal kappa and lambda light chains, unchanged by pronase digestion. A representative electron micrograph is below.
Figure 1:
Which is your next step?
- Order a bone marrow biopsy
- Examine fat pad aspirate for Congo red stain
- Perform age-appropriate cancer screening
- Perform immunohistochemistry on the tissue for DNAJB9
- Begin treatment with rituximab
References
- Andeen, Nicole K, Han-Yin Yang, Dao-Fu Dai, Michael J. MacCross, and Kelly D. Smith. "DnaJ Homolog Subfamily B Member 9 Is a Putative Autoantigen in Fibrillary GN." Journal of the American Society of Nephrology 29, no. 1 (2017): 231–39. doi: 10.1681/ASN.2017050566
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ASN's Board Review Course & Update (BRCU) is the gold standard to maximize your readiness for the ABIM Nephrology Board certification and recertification exams. This course also provides a comprehensive and essential update for practicing nephrologists and healthcare professionals.
