Investigations of bone disorders which are often inherited have yielded important insights in the molecular mechanisms of bone development, osteoporosis and osteoarthritis. However, these studies have been hampered by the lack of available patients and affected families. To overcome this limitation, we have investigated mice treated with the chemical mutagen N-ethyl-N-nitrosourea (ENU) for hereditary bone disorders. Mice were kept in accordance with national welfare guidelines and project license restrictions. At 12 weeks of age, all mice underwent phenotypic assessments that included dysmorphology, radiography and serum biochemistry. These processes identified a mouse mutant that presented with hyperphosphataemia and progressive ectopic calcification. This phenotype was inherited in an autosomal recessive manner. Histological analysis revealed calcification in multiple tissues that included striated muscle, kidney and testis. These features are consistent with familial tumoural calcinosis (FTC) which in man is caused by mutations in fibroblast growth factor 23 (FGF23), KLOTHO, or N-acetylgalactosaminyltransferase 3 (GALNT3). DNA sequence analysis of the mouse homologous genes identified a T to A transversion at nucleotide 1765 of the Galnt3 gene. This altered a highly conserved tryptophan (Trp) residue at position 589 to an arginine (Arg) residue. The presence of this missense Trp589Arg mutation was confirmed using the amplification refractory mutation system (ARMS) PCR technique. ARMS-PCR was performed on genomic DNA using two primer pairs to respectively amplify the wild type and mutant alleles, followed by agarose gel electrophoresis. Heterozygous (+/−) mice were phenotypically normal whilst homozygous (−/−) mice had hyperphosphataemia in association with calcinosis. Thus, we have established a mouse model for autosomal recessive FTC. These results will help to increase our understanding of the molecular mechanisms of FTC and provide a useful model for investigating novel treatments.