BONE-MINERAL DENSITY IN FELINE MUCOPOLYSACCHARIDOSIS-VI MEASURED USING DUAL-ENERGY X-RAY ABSORPTIOMETRY

Dual-energy X-ray absorptiometry (DXA) was used to determine the in vi vo bone mineral density (BMD) and bone mineral content (BMC) of lumbar vertebrae in six cats affected with the inherited lysosomal storage d isease mucopolysaccharidosis VI (MPS VI). DXA was also performed on MP S cats that had a bone marrow transplant (BMT) and total body irradiat ion (TBI) (MPS + BMT; n = 7), normal cats that had a bone marrow trans plant, and TBI (control + BMT; n = 8) and normal cats (control; n = 14 ). Following euthanasia, one of the lumbar vertebrae that had been sca nned (L5) was harvested and bone volume (BV/TV%) was determined by his tomorphometry. The in vivo BMD and BMD measurements were compared with the BV/TV%. There was a greater BMD and BMC in the MPS + BMT cats com pared with the MPS cats but the difference was not statistically signi ficant. However, there was a greater BV/TV% in the MPS + BMT cats comp ared with the MPS cats and the difference was significant (P = 0.0152) . Correlation between the noninvasive in vivo DXA measurements of BMD and BMC and the BV/TV% was significant (r(2) = 0.767, P < 0.0001; r(2) = 0.504, P < 0.0001). Noninvasive in vivo DXA was a rapid and precise method for measuring the lumbar BMD and BMC in cats and it correlated well with histomorphometric determination of bone mass. Further, the response of inherited storage diseases such as MPS VI to therapy, such as BMT, could be monitored in a longitudinal fashion using DXA.