Blackfoot disease in Taiwan: a 30-year follow-up study.

Blackfoot disease is an endemic peripheral vascular disease found among the inhabitants of a limited area on the southwest coast of Taiwan, where artesian well water with a high concentration of arsenic has been used for more than eighty years. The natural history of blackfoot disease, based on a prospective study of 1,300 patients, is presented. The overall male/female ratio was 1.5:1. Although the clinical onset was usually insidious, it may be quite sudden and almost always begins with numbness or coldness in one or more extremities, usually the feet. Ultimately, rest pain develops and progresses to gangrene. In this series, 68% of the patients underwent spontaneous or operative amputation, and the reamputation rate was 23.3%. Lower extremity involvement in blackfoot disease was observed in 97.7% of the cases. The average annual rate for major amputation was 3.81 per 100 patient-years. The factors influencing the prognosis, such as amputation in relation to age and disease onset, are analyzed. The case fatality rate was 66.5% during thirty years; 44% of these were cardiovascular deaths. The annual death rate was 4.84 per 100 patient-years. Other reported case fatality rates for vascular insufficiency are reviewed. A dose-response relationship between blackfoot disease and the duration of water intake was also noted. The survival rates after the onset of blackfoot disease were: five years, 76.0%; ten years, 59.5%; twenty years, 38.2%; thirty years, 28.6%. The 50% survival point was 13.5 years after onset of the disease.