Abstract: PUB013
Cystatin C Limitations in Kidney Function Assessment in Patients with Chronic Myelomonocytic Leukemia
Session Information
Category: Acute Kidney Injury
- 102 AKI: Clinical, Outcomes, and Trials
Authors
- Bengelloun Zahr, Soufiane, Department of Internal Medicine, Rochester General Hospital, Rochester, New York, United States
- Salih, Huda Faisal Sidahmed, Department of Internal Medicine, Rochester General Hospital, Rochester, New York, United States
- Hix, John Kevin, Division of Nephrology, Rochester General Hospital, Rochester, New York, United States
Introduction
Cystatin C is increasingly used as an alternative to creatinine for estimating glomerular filtration rate (eGFR), particularly in patients with low muscle mass. However, cystatin C levels may be influenced by nonrenal factors such as inflammation, malignancy, and immune activation. Chronic myelomonocytic leukemia (CMML) is characterized by persistent monocytosis and systemic inflammatory activity, which may affect cystatin C reliability. Data on the accuracy of cystatin C–based eGFR in CMML are limited.
Case Description
Case Presentation:
78-year-old woman with history of: Chronic myelomonocytic leukemia; Monoclonal gammopathy of undetermined significance; Extranodal marginal zone lymphoma of the orbit; Longstanding monocytosis and chronic anemia for >10 years; Recent progression of anemia prompted further evaluation; Serum protein electrophoresis: monoclonal protein 2.3 g/dL; Bone marrow biopsy: CMML with 5–10% plasma cell involvement
Renal history:
Chronic kidney disease with recurrent membranous glomerulonephritis
Kidney biopsy confirmed membranous nephropathy
Currently receiving rituximab
Renal function assessment:
Creatinine: 0.5 mg/dL → eGFR >60 mL/min/1.73m2
Cystatin C: 1.44 mg/L → eGFR 42 mL/min/1.73m2
Absolute monocyte count: 1.2 ×10^3/L
→ Marked discordance between creatinine- and cystatin C–based eGFR
Further evaluation:
Measured GFR (iothalamate): 71 mL/min/1.73m2
Result aligned more closely with creatinine-based estimate
Discussion
- Cystatin C is commonly used as an alternative marker of kidney function and is less dependent on muscle mass than creatinine
- However, cystatin C is not a purely renal biomarker and may be influenced by: Inflammation, Malignancy, Immune cell activity
- CMML is characterized by: Persistent monocytosis, Dysregulated innate immune signaling, Chronic inflammatory state
- Cystatin C is a cysteine protease inhibitor that regulates cathepsins, which are active in monocytes and macrophages
→ In CMML, increased monocyte activity may alter cystatin C levels independent of kidney function
- In this case:
Cystatin C–based eGFR suggested reduced kidney function (42)
Measured GFR (71) demonstrated preserved renal function
Creatinine-based eGFR aligned more closely with measured GFR
→ Suggests cystatin C overestimated the degree of kidney dysfunction
- When creatinine- and cystatin C–based eGFR are discordant, direct measurement of GFR should be considered
Acknowledgment
We would like to thank the Department of Internal Medicine and the Division of Nephrology at Rochester General Hospital for their support and guidance.