Case 18 Answer

Did you think sacroiliitis? How extensive is the abnormality on the left? Does sacroiliitis extend down into the acetabulum or involve the iliac crest?

Does this help?

much more diffuse cortical thickending and patchy sclerosis/lucencies throughout the medullary cavity

Answer: Paget’s disease of the pelvis

reference: https://radiopaedia.org/articles/paget-disease-of-bone-2

I’ve seen this missed MANY times on lumbar spine X-rays. Don’t forget the pelvis is partially included on lumbar X-rays! Now, admittedly this is commonly asymptomatic and may be a total incidentaloma, but it still deserves mention for further workup as necessary