[Case of pseudohypercreatininemia associated with monoclonal IgM gammopathy].

An 80-year-old man with well controlled hypertension for eight years and monoclonal IgM gammopathy was referred to our hospital in May 2010 due to persistent elevation of serum creatinine(s-Cr). At our hospital, urine and blood tests showed no abnormal findings as BUN and Cr were 15.0 mg/dL and 0.91 mg/dL, respectively. In contrast the referring hospital had obtained values of 10.4 mg/dL and 4.8 mg/dL, respectively. This discrepancy was replicated when s-Cr was measured in another sample from this patient using the enzyme assay kits employed by the referring hospital and our hospital. High-performance liquid chromatography (HPLC), which is the standard method for measuring s-Cr, gave a value in the normal range. After removing high molecular weight proteins (>3,000 D)from the serum sample, the s-Cr levels measured with the respective kits were similar. Since elevation of s-Cr was linked to that of IgM at the referring hospital, we diagnosed the patient as having pseudohypercreatininemia with monoclonal IgM gammopathy.