Urinary N-acetyl-beta-D-glucosaminidase as an indicator of tubular damage in multiple myeloma

In 34 patients with multiple myeloma we have studied urinary N-acetyl-beta-D-glucosaminidase (NAG) as an index of tubular injury and related it to urinary light chain excretion and serum creatinine. Our results confirm the association of light chain proteinuria with both tubular damage and global renal impairment, but show that not all light chains are nephrotoxic. Tubular damage occurs independently of global renal impairment. Clinically, urinary NAG appears to be a useful index of early tubular damage in multiple myeloma.