PAGET'S DISEASE

What is Paget's Disease?

Paget's disease, or osteitis defonnans (as Sir James Paget described it in 1877), is a chronic bone disorder which occurs when the normal process of bone re-modelling goes out of control, resulting in the formation of new, abnormally structured, bone. Excessive bone breakdown and formation makes bone dense but fragile.

These processes may occur in one or many parts of the skeleton and can result in weakened, enlarged or misshapen bones, which may be painful, press on neighbouring nerves, or fracture easily. Enlargement of the skull with varying degrees of deafness is common and, when the long bones of the leg are involved, bowing deformity may occur. Joints also become involved, because of the unequal stresses imposed by the bent bones. It is usually a very slowly progressive disorder and is rarely fatal.

Who gets it?

It is estimated that between 4 - 8% of people in the United Kingdom over 40 years of age are affected to some degree by Paget's disease. There is also a high incidence of the condition in Europe, USA, Australia, and New Zealand. There are, however, some marked variations in frequency around the world and between races; for instance, it is extremely rare in Scandinavia and the Far East.

Paget's disease rarely affects young people and increases in frequency with advancing age. Fortunately, only a small proportion of all patients with Paget's disease experience significant symptoms.

Current research into Paget's disease suggests that it may be caused by a virus, the identity of which is as yet unknown, although the condition is certainly not "infectious" in the usual sense of the term. So far there is no conclusive evidence to suggest it is hereditary, although it often occurs in more than one family member.

What tests will the Doctor want to do?

Paget's disease is often detected by chance when a person has a routine x-ray or blood test for another reason. Clinical features such as curved legs, bent spine, bone thickening and enlargement of the skull, can be highly suggestive of the disease, but are present in only a minority of patients.

Laboratory tests of blood, available through your doctor, can indicate the presence of Paget's disease. The level in the blood of alkaline phosphatase indicates that bone forming cells (osteoblasts) are more active than normal.

Although x-rays are used to confirm the presence of Paget's disease in a particular bone when the disease is first diagnosed, a bone scan may also be carried out to check the extent and activity of the disease. As with the urine test to check the levels of hydroxyproline (which reflects the level of activity of bone resorbing cells (osteoclasts)), this is usually only done in specialised clinics.

What is the treatment?

Although it is now over 100 years since the disease was first identified it has only been in the last 10 to 20 years that medical science has produced positive results in the treatment of the condition.

Treatment is varied and depends on a full assessment of the individual patient. When patients have no pain or other symptoms, then treatment is generally not prescribed. Where patients suffer mild bone pain, simple analgesics (painkillers) may be all that is necessary, but if these prove ineffective or if symptoms become more acute then there are several other effective forms of treatment.

The most widely used drugs in recent years (and the only two currently licensed for Paget's disease) have been Calcitonin, (given by injection) and etidronate disodium (Didronel) (given by mouth).

Didronel belongs to a group of drugs known as bisphosphonates of which Aredia (better known as Pamidronate or APD) is one. Pamidronate/APD is administered by intravenous infusion (i.e. through a drip into the arm) over a period of several hours. Hospital admission is not necessary for this and patients are usually treated on a day-patient basis.