A 35-year-old patient with chronic ear discharge undergoes high-resolution CT mastoid, which reveals an erosion of the scutum (spur of Henle), soft tissue in Prussak's space, and lateral semicircular canal dehiscence. Which mechanism best explains the bone erosion by cholesteatoma?
- A Direct pressure necrosis only
- B Enzymatic osteolysis via collagenases and cytokines (IL-1, TNF) from keratinocytes and perimatrix ✓
- C Osteoclast activation by PTH-related peptide alone
- D Bone destruction caused entirely by secondary bacterial infection
Correct answer: B. Enzymatic osteolysis via collagenases and cytokines (IL-1, TNF) from keratinocytes and perimatrix
Explanation
Cholesteatoma causes bone erosion through enzymatic osteolysis mediated by collagenases, acid phosphatase, and pro-inflammatory cytokines (IL-1, IL-6, TNF-alpha) released by the hyper-proliferating keratinocytes and the perimatrix. Although pressure necrosis and secondary infection contribute, enzymatic mechanisms are the principal drivers of the aggressive bony destruction characteristic of cholesteatoma. Lateral semicircular canal erosion is a recognized serious complication.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.