Acute Kidney Failure: When Multiple Myeloma Doesn´t Give Additional Clues

Multiple myeloma (MM) is characterized by a proliferation of malignant plasma cells and a subsequent overabundance of monoclonal paraprotein. This disease commonly presents with hypercalcemia, kidney failure, anemia, and bone lesions. Acute kidney failure (AKF) as an initial presentation of MM has rarely been reported. Herein, we present a case of a 49-year-old female who was admitted to our intensive care unit (ICU) for AKF in June 2017. The patient was admitted to our emergency room (ER) with abdominal pain and biliary vomiting within six days. From the laboratory tests, we highlight a serum creatinine of 19 mg/dl and urea of 377 mg/dl. The physical examination was globally unremarkable. Once clinically stable, she was admitted to our infirmary with a creatinine of 8.00 mg/dl. The patient underwent an extensive study: markers for hepatitis B and C, human immunodeficiency syndrome (HIV), and autoimmune markers were all negative; renal ultrasound, abdominal and pelvic CT had no relevant alteration; and the skeletal survey had no significant change. Peripheral blood smear showed no abnormalities. Serum immunoglobulin analysis revealed an elevated immunoglobulin A (IgA). Serum protein electrophoresis showed a monoclonal spike and urine protein electrophoresis showed an increased amount of protein consistent with Kappa light chains. The Kappa:Lambda chain ratio was increased. In order to understand the etiology of this AKF, we ended up performing a kidney biopsy, which was compatible with a myeloma kidney. The patient was transferred to the Portuguese Oncology Institute in Porto and initiated chemotherapy. Two months after the hospital discharge, creatinine levels were stable around 1.5 g/dL. This case illustrates AKF as the initial and sole presentation of MM. This presentation, even though previously reported, is very uncommon, especially considering that it occurred in a young woman and it was associated with light chain precipitation of IgA. MM is an important differential diagnosis in AKF, particularly when excluded pre and post-renal etiologies. Although being an invasive procedure with inherent possible complications, a kidney biopsy is still a very important procedure that was essential in this case to achieve a final diagnosis and, therefore, the patients' treatment.