Nephrogenic systemic fibrosis: history and epidemiology.

Nephrogenic systemic fibrosis (NSF) is a new disease; the first case was diagnosed in 1997. It took 9 years before an association between NSF and gadolinium-based contrast agents (Gd-CAs) was identified. Gadolinium has several advantages for use in relation to enhanced MRI, but it is also a toxic heavy metal. For nearly 20 years, it was believed that Gd-CAs were safe, and they were used liberally. The prevalence of NSF cases varies between the various Gd-CAs, and adequate documentation of NSF cases after exposure to extracellular Gd-CAs remains a problem. All evidence points toward the fact that the real number of patients who have NSF has not been accurately totaled; the disease seems to be underdiagnosed for various reasons.