Biomarkers and imaging in non-malignant and malignant osteomalacia

Deoxypyridinium (DPD) cross-links are a specific parameter for collagen typ e I degradation. We report the longitudinal tracking of DPD in relation to other bone markers and imaging techniques in a patient with osteomalacia an d secondary hyperparathyroidism from reduced light exposure due to attire. This patient was first admitted for diffuse skeletal pain. X-rays showed ge neral demineralization and Looser's transformation zones in the neck of the left femur. MRI examinations of the pelvis and the proximal femora demonst rated bilateral signs of acute sacroiliitis, as well as edema-like lesions in the femoral heads and necks bilaterally. The baseline parathyroid hormon e level was 8 times higher than the normal upper limit, whereas 25-hydroxyv itamin D and 1,25-dihydroxyvitamin D levels were significantly reduced. A 7 -fold increase in free urinary DPD and a 17-fold increase in bone-specific alkaline phosphatase (bone-AP) were also measured. Percutaneous transiliac bone biopsy revealed markedly increased osteoidosis. Osteomalacia was diagn osed due to chronically reduced sun exposure caused by restrictive attire, and cholecalciferol substitution therapy was begun. After a follow-up of 28 weeks, non-specific parameters of bone turnover (parathyroid hormone, tota l alkaline phosphatase, serum calcium and serum phosphate) had normalized, while DPD, as a specific bone degradation marker, and bone-AP, as a bone fo rmation parameter, both remained elevated. This example underlines the vali dity of DPD and bone-AP as indicators of increased bone metabolism: not onl y were they the parameters with the highest baseline deviation, but they we re also the last to normalize.