Hypertrophic Pulmonary Osteoartropathy (HPO) is a peculiarity whereby any mass in the chest - usually a large single mass - triggers periosteal changes and arthritis typically of the forelimb, in my experience. And often with a typical paillisade appearance to the changes. These are not as dramatic as the periosteal changes seen with my other favourite Craniomandibular Osteoarthropathy where that occurs on the mandible.

 These first three images show the changes in elbow and lower forelimb. In this patient the elbow changes are particularly severe. This GSDX 12yrs old was presented with progressive lameness left fore and on questioning the onwer they also reported a cough. I've been looking for a case of Hypertrophic Pulmonary Osteoarthropathy for many years - after I missed one picked up on referral - although to be fair to me that case was more subtle and the referral centre admitted their chest x-ray was a happy accident of poor positioning - This case had all the right clues. And the chest x-rays were very obvious. In the case of this patient, age and reality dictated that it was  matter of managing him as long as possible with pain control. Otherwise the ideal would be some biopsy work on the chest mass with a view to removal if possible.