Clinical History
23-year-old woman with right great toe pain.
Diagnosis: Calcific Periarthritis of the First MTP Joint
Calcific periarthritis is caused by calcium hydroxyapatite deposition in a periarticular location, inciting a marked localized inflammatory reaction.
Sonographic appearance is of periarticular echogenic mineralization which may have posterior shadowing (not seen in this case), which could be mistaken for gouty tophus (though this would be rare in a young woman).
Correlation with x-ray is helpful, as calcium hydroxyapatite has a characteristic radiographic appearance.