The clinical course of all Itai–itai disease
patients and persons requiring observation was
examined as the research project conducted by the
Research Committee for Itai–itai Disease organized by
the Japan Environment Agency from 1989. The clinical
course of 13 cases showed that renal tubular dysfunction
had deteriorated culminating in end-stage renal
failure. After the serum creatinine exceeded 2.5 mg/dl
death ensued in 3–4 years (Kasuya, 1999).