Biomarkers and imaging in non-malignant and malignant osteomalacia.

Deoxypyridinium (DPD) cross-links are a specific parameter for collagen type I degradation. We report the longitudinal tracking of DPD in relation to other bone markers and imaging techniques in a patient with osteomalacia and secondary hyperparathyroidism from reduced light exposure due to attire. This patient was first admitted for diffuse skeletal pain. X-rays showed general demineralization and Looser's transformation zones in the neck of the left femur. MRI examinations of the pelvis and the proximal femora demonstrated bilateral signs of acute sacroiliitis, as well as edema-like lesions in the femoral heads and necks bilaterally. The baseline parathyroid hormone level was 8 times higher than the normal upper limit, whereas 25-hydroxyvitamin 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 diagnosed 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, total alkaline phosphatase, serum calcium and serum phosphate) had normalized, while DPD, as a specific bone degradation marker, and bone-AP, as a bone formation parameter, both remained elevated. This example underlines the validity of DPD and bone-AP as indicators of increased bone metabolism: not only were they the parameters with the highest baseline deviation, but they were also the last to normalize.

MR imaging of septic sacroiliitis.

OBJECTIVE: To investigate the diagnostic value of magnetic resonance (MR) imaging in detecting septic sacroiliitis and to determine whether the MR characteristics allow this entity to be differentiated from sacroiliitis in spondylarthropathy (SpA). PATIENTS AND DESIGN: The imaging findings of 11 patients with septic sacroiliitis were retrospectively analyzed by two experienced radiologists. Radiographic surveys of the pelvis as well as computed tomography (CT) and MR images of the sacroiliac joints were available in all cases. Seven of the patients additionally underwent a follow-up MR examination. The MR imaging protocol comprised combinations of coronal and transverse T1-weighted spin-echo (SE) or fast SE sequences, T2-weighted gradient-echo (GE) sequences and short tau inversion recovery sequence (STIR) sequences as well as dynamic contrast-enhanced T1-weighted acquisitions. RESULTS: Three patients with a short disease history showed anterior and/or posterior subperiosteal infiltrations ("lava cleft phenomenon"), transcapsular infiltrations of juxtaarticular muscle layers, which obscured the fasciae, and periarticular bone marrow edema. The eight patients with more advanced stages of sacroiliitis additionally showed abscess formation, sequestration, and erosion. At follow-up MR examination (n=7) under systemic antibiotic treatment, the morphologic characteristics showed progression (n=1), regression (n=4), unchanged findings (n=1), or a mixed response (n=1). Clinical improvement precedes resolution of the MR findings. CONCLUSIONS: Anterior and/or posterior subperiosteal infiltrations and transcapsular infiltrations of juxtaarticular muscle layers were depicted in all patients. These MR imaging findings are characteristic of septic sacroiliitis and may be used to differentiate this entity from sacroiliitis in SpA.