Diagnosis of light chain cast nephropathy through immunostaining of the urine: Perfecting the "liquid biopsy"
No Thumbnail Available
Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Light chain (LC) cast nephropathy is the main cause of kidney injury and an important determinant of poor survival in patients with multiple myeloma (MM). It is usually suspected when an MM patient with elevated serum concentration of free LC presents kidney failure, but it often requires confirmation by kidney biopsy. We report the case of a 73-year-old woman who presented with fatigue, weight loss, and constipation. Laboratory exams revealed anemia, hypercalcemia, and kidney failure. Urine sediment analysis demonstrated irregular crystalline "waxy type" casts. With the hypothesis of LC cast nephropathy, immunostaining of the urine sediment was performed. The analysis revealed several rectangular and irregular casts with intense and bright stain for lambda LCs only. A myelogram was performed, showing extensive occupation of the bone marrow by plasma cells; and immunofixation in urine and serum revealed monoclonal IgG-lambda component, confirming the diagnosis of IgG-lambda MM. This case highlights the potential utility of the urine sediment analysis and immunostaining as a reliable non-invasive alternative method for diagnosis of cast nephropathy in patients with monoclonal gammopathies.
Description
Keywords
light chain cast nephropathy, immunoglobulin light chains, multiple myeloma, acute kidney injury