Axial osteomalacia with sacroiliitis and moderate phosphate diabetes: Report of a case

We report a new case of axial osteomalacia diagnosed in a 51-year-old white Caucasian male, made particular by its association with sacroiliitis, posi tive HLA-B27 antigen, and also moderate phosphate diabetes responsible for a decreased appendicular bone mass. The diagnosis was suspected when X-my e valuation showed increased density and coarse trabeculation mainly involvin g the pelvis and spine Dual energy X-ray absorptiometry confirmed the eleva ted bone density at the lumbar spine (T score: +1.92) contrasting with a de creased bone mass at. the femoral neck (T score: -2.33). The diagnosis was confirmed by histomorphometry of the iliac crest showing marked thickening of the cortices (2190 mu m +/- 0.574, N = 780 +/- 40) and an increased trab ecullar bone volume (33.24%, N = 14 +/- 3). Osteoid parameters were also ma rkedly increased with an osteoid volume of 2.1% (N = 1.2 +/- 0.5) and a mea n osteoid thickness of 28. 7 mu m (N = 13 +/- 2.5), with a normal bone fluo ride content (0.082%, N < 0.10). Bone resorption as assessed on bone biopsy and by the measurement of markers of bone remodeling (serum procollagen ty pe I C-terminal telopeptide and 24 hr urinary cross-laps to creatinine rati o) was increased. This latter finding was not necessarily due to axial oste omalacia and could be the consequence of moderate phosphate diabetes. The p atient was treated with calcitriol which was promptly discontinued due to g astrointestinal symptoms and replaced by calcidiol without any significant effect on the low back pain.