This project provides high-resolution LC-MS/MS datasets dedicated to the de novo sequencing of monoclonal immunoglobulin light chains (FLCs) associated with light chain proximal tubulopathy (LCPT). LCPT is a rare renal manifestation of plasma cell dyscrasias, characterized by proximal tubule dysfunction. The disease encompasses both crystalline and non-crystalline variants: while the former is defined by the formation of organized intracellular crystals, the latter presents as tubular dysfunction in the absence of observable inclusions.