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Abstract Background Elevated creatinine concentrations often indicate acute renal injury and renal biopsies are considered in this situation. However,pseudohypercreatininemia is potential cause of elevated creatinine concentrations, and invasive interventions should be avoided. Case presentation A 54-year-old woman underwent surgery for descending aortic dissection.Nine days postoperatively, her creatinine concentration increased from 1 mg/dl to 5.78 mg/dl (normal range, 0.47–0.7 mg/dl). Azotemia and hyperkalemia were absent and physical examination findings were unremarkable. Cystatin C concentration was 1.56 mg/l (normal range, 0.56–0.8 mg/l) and pseudohypercreatininemia was suspected. Testing with different reagents showed a creatinine concentration of 0.84 mg/dl. Immunoglobulin (Ig)G was markedly elevated, and creatinine and IgG fluctuated in parallel, suggesting the cause of the pseudohypercreatininemia. IgG4 was also elevated at 844 mg/dl. Immunosuppressive steroid therapy effectively decreased the IgG concentration and resolved the pseudohypercreatininemia. Conclusions In cases of elevated creatinine concentration with the presence of abnormal proteins, pseudohypercreatininemia should be considered. We report a rare case of pseudohypercreatininemia caused by polyclonal IgG.

Fabry disease (FD) is a multi-organ disorder caused by a deficiency of alpha-galactosidase (α-GLA) or reduced activity of the enzyme due to mutations in the GLA gene on the X chromosome, making it an X-linked hereditary disease. A 37-year-old man previously diagnosed with sudden deafness and cardiac hypertrophy was referred to our department after an abnormal urine finding during a public health checkup. A renal biopsy revealed characteristic findings, and he was diagnosed with FD with a novel GLA abnormality (c.714dupT (p.I239Yfs*11)). We are currently administering enzyme replacement therapy (ERT) with agalsidase α. This case shows that a novel genetic abnormality in FD can be overlooked for 37 years, even in the presence of typical symptoms. The significance of a renal biopsy in diagnosing FD is emphasized, highlighting the crucial role of nephrologists. [ABSTRACT FROM AUTHOR]