High serum cystatin C levels in juvenile myelomonocytic leukemia patients without abnormal kidney function

Background In pediatric cancer patients, the estimated glomerular filtration rate based on serum cystatin C (CysC) was reported to be suitable for estimating kidney function because of low serum creatinine (Cr) and high serum beta(2)-microglobulin. Recently, however, serum CysC levels have been reported to be elevated in some cancer patients other than those with juvenile myelomonocytic leukemia (JMML), regardless of normal kidney function. Case reports We describe two pediatric cases of JMML with an elevated serum CysC level. Urinalysis tests showed no abnormalities and no evidence of nephritis or nephropathy, and there were no findings indicating abnormal kidney function, such as Cr clearance in one case or the estimated glomerular filtration rate based on serum Cr in both cases, except for the serum CysC levels. There were no other causes of a high serum CysC level, including hyperthyroidism and steroid administration. The patients were treated with a conventional dosage of drugs, and their serum CysC levels decreased to the normal range when they were in complete remission after treatment. Conclusion An elevated serum CysC level may reflect tumor burden independent of kidney function in JMML patients. Therefore, creatinine or inulin clearance should be determined to more accurately estimate kidney function for administering an optimal dose of anticancer drugs. In addition, a high serum CysC level may be a potential biomarker of cancer progression.

Automated summary

This study reports two cases of elevated serum CysC levels in JMML patients. Despite normal kidney function, it may be associated with tumor burden. It is recommended to determine creatinine or inulin clearance to accurately estimate kidney function when administering anticancer drugs.