Rare Causes of Musculoskeletal Pain: Thinking beyond Common Rheumatologic Diseases

Figure 1

The X-ray images from our XLH case (a–c). Preoperative films of the left hip (a) demonstrate prominent enthesophytes of the left iliac wing and trochanters, initially misdiagnosed as sequelae of AS. The femoral bowing seen would be atypical of AS. The patient had a successful total hip arthroplasty of the left hip (b), which was later complicated by pseudofracture ((c), arrow) characteristic of XLH but not AS. To further illustrate how XLH can mimic spondyloarthritis on imaging, lateral (d) and anterior posterior (e) thoracic spine films demonstrate flowing syndesmophytes and a lateral ankle X-ray scan shows an Achilles enthesophyte (f).