<unk>  is diagnosed by findings on x-ray studies. Radiographs of the spine will show abnormal bone formation (ossification) along the anterior spinal ligament. The disc spaces, facet and sacroiliac joints remain unaffected. Diagnosis requires confluent ossification of at least four contiguous vertebral bodies. Classically, advanced disease may have "melted candle wax" appearance along the spine on radiographic studies. In some cases,<unk>  may be manifested as ossification, or enthesis, in other parts of the skeleton. The calcification and ossification is most common on the right side of the spine. In people with dextrocardia and situs inversus this calcification occurs on the left side. File:Thoracic spine Lat.Confluent ossification of multiple contiguous vertebral bodies in<unk>  <unk>  File:Thoracic spine AP.alt="Melted candle wax" appearance of calcification and ossification in<unk>  <unk> . Note the preponderance on the patient's left side (right side of image). File:Calcification in Achilles tendon insertion and calcaneal spur.Ectopic calcification and new bone formation in<unk>  <unk>  File:Ossifikation Ligamentum longitudinale posterius HWS bei<unk>  - CT axial und sagittal - 001.Ossification of the posterior longitudinal ligament in<unk>
Diffuse idiopathic skeletal hyperostosis
Hereditary multiple exostoses
Giant-cell tumor of bone
Fibrous dysplasia of bone
Gerodermia osteodysplastica
Paget's disease of bone
Malignant infantile osteopetrosis
Pycnodysostosis