Most patients with NFD have undergone hemodialysis for renal failure, some have never undergone dialysis and others have received only peritoneal dialysis. Many patients have taken immunosuppressive medications and have other diseases, such as hepatitis C. Four of the five FDA-approved gadolinium contrast agents have been principally implicated in NFD, including Omniscan, Multihance, Magnevist, and OptiMARK.