[A case of pseudohypercreatininemia in a patient suffering from macroglobulinemia]

A 56-year-old man with chronic hepatitis was admitted to the nephrology unit because of a progressive increase in serum creatinine(Cr). Blood Urea Nitrogen(BUN) and Cr, measured by the enzymatic method, were 15 and 2.0 mg/dl, respectively, in 1999, and changed to 17 and 3.8 mg/dl, respectively, on February 2000. However, urinalysis did not show any abnormalities. Hypergammaglobulinemia and hypocomplimentemia were observed, but the immune complex level was normal. Major self-antibodies were all negative. MRI renal angiography and renoscintigram, respectively, showed little abnormality. Renal biopsy performed in April revealed no abnormalities. Treatment was started with the administration of steroid, anticoagulation agents and activated charcoal under the hypothesis of serious glomerulonephritis. Cr and Cr clearance (Ccr) aggravated to 5.4 mg/dl and 11.9 ml/min in April, and then returned to 2.7 mg/dl and 22.8 ml/min in May, however, steroid and anticoagulation administration were terminated because the biopsy findings were identified as normal. When cryoglobulinemia was found in August, serum Cr was found to be 1.0 mg/dl when measured by a modified Jaffe's method. Clearance test of p-aminohippurate sodium and sodium thiosulfate, i.e., CPAH and CTHIO, showed normal renal function. After the detection of macroglobulinemia(IGM-lambda), the patient has been treated with the administration of melphalan and prednisolone in the hematology unit since July 2001. Analysis of plasma amino acid showed a high glutaminic acid (Glu) level before the subsequent chemotherapy and dissolution. His serum Cr was 0.9 mg/dl even when measured by the enzymatic method after chemotherapy. A previous report referred to the possibility that enzymatic measurement is affected by the high proline level because of its structural resemblance to Cr, however, the high Glu level in this case did not seem to have this effect because of less resemblance to Cr. Therefore, paraproteinemia is thought to affect enzymatic Cr measurement, and CPAH and CTHIO should be used when as abnormally high Cr level appears.