Paget’s disease

This older male had been complaining for a number of years of headache, back ache, hip and knee pain — not uncommon symptoms as we get older. The diagnosis of Paget’s disease of bone is easy to establish once that diagnosis is under consideration. Given the symptoms suggestive of degenerative joint disease (DJD) and in the absence of obvious skeletal deformity, the only clue that had been missed was an elevated alkaline phosphatase, stable at ~ 300-400 for a number of years. Once confirmed by bone scan and X-ray, the management is straightforward — a short course of IV bisphosphonate with the number and duration of infusions dependent on the bisphosphonate selected.

The first treatment usually lowers the phosphatase by 50% or more, and it is not necessary to keep treating until the level is back to normal. More aggressive therapy may be appropriate if the baseline phosphatase is in the thousands. I see no justification for measuring bone-specific alkaline phosphatase unless, after radiologic confirmation of the diagnosis, the total alkaline phosphatase is only minimally elevated, and even then, I am not sure it is necessary. Likewise, there is little indication to measure or monitor other markers of bone remodeling. Treatment of symptomatic patients is always indicated. In asymptomatic patients in whom the phosphatase is markedly elevated (greater than arbitrarily twice the upper limit of the reference interval), treatment is appropriate. Many patients will require only one course of IV bisphosphonate, but the phosphatase should be monitored at six monthly intervals or when symptoms recur, and re-treatment is appropriate if there is a substantial rise.

The clinical problem in this case is that he does indeed have DJD secondary to his age and Paget’s, and the symptoms did not abate much with therapy although his alkaline phosphatase returned to just above normal. His headaches did decrease in frequency and intensity. Hindsight is 20/20 vision, and noting the elevated phosphatase should have brought this possibility to attention earlier, but that too might not have made a difference to the outcome because he did not present with skeletal pain or deformity, just joint aches and pains. The asymmetry of the DJD is perhaps the only clinical symptom that might have suggested something beyond simple wear and tear on the joints.

The symptoms and complications of Paget’s are a function of the skeletal parts involved in the disease. When a vertebral body is involved, neurologic symptoms may occur as the vertebra expands and impinges on the spinal cord. Metastatic disease may be the first thing that comes to mind when the spine X-ray is taken because the affected vertebra looks quite abnormal. Paget’s, but not sclerosing metastases as might be seen in prostate cancer, increases vertebral body dimensions in both the anterior-posterior and lateral view. Involvement of the proximal femur may present not with joint pain but intense heat over the affected area. A bowing deformity of one leg is another indication of possible Paget’s — again asymmetry is the clue. In the long bones, Paget’s seems to always appear at the end of the bone, proximal more often than distal, and to my understanding, the lesion never appears first in the shaft.

Paget’s can be a monostotic or polyostotic condition and may be asymptomatic for some time. When the diagnosis is made as an incidental finding on an X-ray taken for other reasons, it is worthwhile to proceed to a bone scan to document the extent of the disease. It is important for you and the patient to know that it is rare for Paget’s to develop in a new skeletal site once the diagnosis has been established. Should a new skeletal lesion develop, it is imperative to seek a cause other than Paget’s, all too often a metastasis.

X-ray of a man with degenerative joint disease and Paget's