The blood biochemistry is normal, including calcium, phosphate & alkaline phosphatase. HLA-B27 and rheumatoid factor are negative.
Diabetes mellitus is commonly associated and a fasting glucose may be elevated.
- blood tests - ESR, CRP, rheumatoid factor, and antinuclear antibody - are normal in DISH
- radiography - AP and lateral spine imaging in patients with DISH demonstrate "flowing candle wax,"
- describes the non-marginal syndesmophytes that project horizontally from the vertebrae and form extra-articular ankylosis
- distinguishable from the vertical "bamboo spine" that forms intra-articular disc space ossification in ankylosing spondylitis (AS)
- increased radiodensity, preservation of facet joints and disc spaces on spine imaging help further distinguish DISH from AS
- may present with osteopenia and degenerative changes - note the association between DISH and low bone density remains controversial
- thoracic spine is most commonly involved in DSH
Reference:
- Belanger TA, Rowe DE. Diffuse idiopathic skeletal hyperostosis: musculoskeletal manifestations. J Am Acad Orthop Surg. 2001 Jul-Aug;9(4):258-67.