AXIAL OSTEOMALACIA - REPORT OF A NEW CASE WITH SELECTIVE INCREASE IN AXIAL BONE-MINERAL DENSITY

Axial osteomalacia was diagnosed in a 60-year-old white Caucasian male , on the basis of X-ray examination showing typical coarsened and spon ge-like appearance of trabecular bone strictly located in the axial sk eleton, Dual energy X-ray absorptiometry demonstrated a marked increas e in axial bone density at lumbar spine levels in both anteroposterior and lateral views (T score: +7.9 and +5.5, respectively), contrasting with normal values at femoral neck, trochanter and midfemoral diaphys is (T score: +0.6, +0.3, and +0.8, respectively). Histomorphometry of iliac crest showed marked thickening of cortices (1730 and 2763 mu m, N = 967 +/- 57), increased trabecular bone volume (28.9%, N = 17.4 +/- 5.6), normal eroded surface (3.5%, N = 3.6 +/- 1.1), and increased os teoid surface and volume (31.6%, N = 15.3 +/- 9.4 and 5.8%, N = 2.8 +/ - 1.8). Osteoid thickness was increased (39.6 mu m N = 10.5 +/- 1.8, u p to 120 mu m in one site) and mineral apposition rate was decreased i n the trabecular sites (0.43 mu m/day, N = 0.72 +/- 0.12, down to <0.2 mu m/day, focally), Bone fluoride content was not increased (0.08%, N < 0.10%). All biochemical parameters of bone metabolism, including se rum osteocalcin, PTH, calcidiol, calcitriol, and renal tubular reabsor ption of calcium or phosphate were normal.