Radiographic examination of the skull may show irregular rarefaction of the calvaria (“salt-and-pepper” skull) and loss of the dense white line cast by the lamina dura surrounding the roots of the teeth. Cortical thinning and fuzzy trabeculae characteristic of both osteomalacia and osteitis fibrosa cystica are seen in radiographs of the long bones, with additional findings of small or large, rarefied, rounded lytic lesions characteristic of brown tumors; “disappearance” of the lateral portion of the clavicle; and subperiosteal resorption of the proximal medial tibia. The most noticeable changes are seen in the bones of the hand, with erosion of the terminal phalangeal tufts and subperiosteal resorption of the proximal and distal phalanges most marked on the radial sides.
For reasons not clearly understood, about 20% of the patients with the combination of chronic renal disease, osteomalacia, and osteitis fibrosa cystica also develop a type of osteosclerosis. Histologic findings reveal an increased number of trabeculae per unit volume rather than a healing of the demineralized bone of osteomalacia (osteoid seams) or an alteration in the resorptive changes of osteitis fibrosa cystica. The disease most commonly affects the subchondral cortices of the vertebrae and the shafts of the long bones, producing a radiographic appearance of alternating light and dark shadows (banded sclerosis, or “rugger-jersey spine”). The small bones or digits of the hands and feet are rarely involved.
Renal adynamic bone disease is characterized by low bone mineral density (BMD) by either dual energy x-ray absorptiometry (DXA) or quantitative computed tomography (QCT) or by low bone turnover on biopsy or suspected by low bone turnover markers (BSAP and PTH), hypercalcemia, and fractures. Renal adynamic bone disease may be “idiopathic,” more often seen in patients with diabetes and on peritoneal dialysis, or iatrogenic from excess lowering of PTH levels by agents that inhibit PTH production (vitamin D analogs or cinacalcet). Recently, the Kidney Disease Improving Global Outcomes (KDOGO) Bone Working Group has published their guidelines on managing these more complex bone and mineral disorders.
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