Circulating Monoclonal Light Chains and Acute Kidney Injury: The Role of the Renal Biopsy with Emphasis on Ultrastructural Evaluation in Assessing and Understanding Renal Injury

Tubular interstitial injury as a consequence of circulating monotypical light chains in patients with an underlying plasma cell dyscrasia may be difficult to identify. Renal involvement is a common early manifestation in these patients, and accurate/careful pathologic evaluation can uncover an underlying plasma cell dyscrasia. While immunofluorescence evaluation can detect monotypical deposition of light chains in the tubular interstitial compartment and may suggest a possible underlying plasma cell dyscrasia, electron microscopic examination is crucial in documenting such involvement. Ultrastructural immunolabeling can help in solidifying the pathological assessment.