Which histologic findings are characteristic of ankylosing spondylitis (AS)?

Updated: Jul 17, 2018
  • Author: Lawrence H Brent, MD; Chief Editor: Herbert S Diamond, MD  more...
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Answer

Histopathologic evaluation is not generally part of the diagnostic workup in patients with ankylosing spondylitis.

The basic pathologic lesion is inflammation at the enthesis (enthesitis), which occurs at the site of insertion of ligaments and tendons into bone. The histologic picture is that of chronic inflammation with CD4+ and CD8+ T lymphocytes and macrophages. Early AS lesions include subchondral granulation tissue that erodes the joint. Over time, fibrosis and ossification occur, which can be seen radiographically as periostitis and ossification at sites of enthesitis, particularly the SI joints, spine, and heels.


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