Tuesday, February 23, 2021

Paget’s Disease of the Spine

 

By Nabil A. Ebraheim MD & Dalton Blood MD


The presence of a white vertebral body on lumbar spine x-ray requires differentiation between Paget’s, Rugger-Jersey spine, and metastatic prostate carcinoma.

Paget’s disease involves abnormal bone remodeling characterized by excessive osteoclast bone resorption followed by increased osteoblast bone formation which is disordered and structurally weaker than normal, healthy bone. The increased bone turnover causes these patients have an increased serum alkaline phosphatase and urinary hydroxyproline and urinary N-telopeptide. Due to rapid, disorganized bone formation, bone samples under the microscope demonstrate a mosaic pattern and cement lines. The increased osteoblast activity can also result in cortical thickening. This cortical thickening increases opacity of the cortex on all sides of the vertebral body combined with vertebral body expansion and coarsened trabeculae makes the vertebra look like a picture frame (“Picture frame vertebra body”). In Paget’s disease the cortex is thickened on all sides of the vertebral body. In contrast, the Rugger-Jersey spine sclerosis only occurs at the superior/inferior vertebral endplates.

Rugger-Jersey spine describes the prominent sub-endplate density at multiple continuous vertebra levels. The alternating sclerotic, lucent appearance on x-ray looks like the horizontal stripes of a rugby jersey.  These pathogenic changes occur due to hyperparathyroidism which leads to increased bone resorption with subsequent loss of bone mass resulting in the lucent areas seen. The dense or sclerotic areas at the superior and inferior vertebral body endplate result from excess osteoid accumulation.

While Paget’s disease lesions can appear osteoblastic, metastatic prostate and breast tumors can also appear as osteoblastic lesions on x-ray. The diffuse and homogeneous increase in opacity of a vertebral body that otherwise maintains its size and contours with no change in the adjacent intervertebral discs is called the “ivory vertebra sign”. This sign often indicates metastatic prostate cancer in adult males or metastatic breast cancer in females. An elevated Prostate-Specific Antigen (PSA) and biopsy can confirm the diagnosis of prostate cancer. The lesion biopsy histology demonstrates adenocarcinoma with gland formation. The key differences between Paget’s disease, Rugger-Jersey spine, and metastatic prostate cancer allow for effective differentiation between these disease processes when presented with a white vertebra x-ray.