Note the significantly elevated calcium content in the muzzle skin of Abcc6−/− mice, either NT or injected with saline, as compared with the WT mice (right panel). Injections of Abcc6−/− mice subcutaneously with 0.01× and 0.12× ETD significantly reduced the calcium content of the muzzle skin as compared with age-matched mice injected with saline. Etidronate treated Abcc6−/− mice at 24 weeks of age demonstrated mineralization similar to Abcc6−/− mice at 12 weeks of age, indicating that ETD prevents further mineralization but does not reverse mineralization that had developed before initiation of treatment. *p < 0.05, **p < 0.01, compared to KO mice at 12 weeks of age; ++p < 0.01, compared to KO mice at 24 weeks of age. Mean ± SE; n = 7–10 mice per group. ETD, etidronate; KO, knockout; WT, wild type; NT, not treated.