Renal tubular acidosis type II secondary to gamma-light chain excretion in an elderly patient with multiple myeloma

A 73-year-old woman was admitted to the geriatric ward of the University of Tokyo Hospital with anemia, osteepeina, and renal dysfunction. Although symptoms typical of multiple myeloma such as punched-out lesions and hyperproteinemia were not found, protein electrophoresis revealed that lambda type Bence-Jones protein was excreted in urine. Multiple myeloma was diagnosed. Furthermore, renal dysfunction was accompanied renal tubular acidosis type II (proximal type). Renal dysfunction in patient with multiple myeloma in usually caused by so-called myeloma casts in the distal tubules, but renal tubular acidosis type II is rarely observed. It is possible that injury of the proximal renal tubular eithelium by Bence-Jones protein resulted in renal tubular acidosis type II in this patient.