In this study we describe an ENU-induced mouse mutant named RENF, presenting with clinical features of failure to thrive, early onset renal failure and interstitial nephritis, due to a Xdh nonsense mutation which is located within the iron-sulphur (2Fe-2S) ferredoxin-type domain close to the N-terminus of XDH (Table 1, Figures 1–, 3). The gene discussed is XDH; the disease is interstitial nephritis.