The importance of urinary immunoglobulin light chain isoelectric point (pI) in nephrotoxicity in multiple myeloma.

There is clinical and experimental evidence to imply that urinary immunoglobulin light chains are nephrotoxic yet some patients pass large amounts for years with little renal damage. Animal experiments suggest that a light chain is more nephrotoxic if it has a high isoelectric point (i.e. is cationic in relation to urine pH). We studied 23 patients with multiple myeloma, measuring light chain excretion rate, light chain isoelectric point (pI) and creatinine clearance. Light chain excretion rate was independent of light chain isoelectric point and did not correlate with creatinine clearance. Light chain isoelectric point correlated with creatinine clearance, suggesting that this characteristic may be an important determinant of the nephrotoxic effect of these immunoglobulin constituents.