Paget’s Disease
Description
Paget’s Disease also known as osteitis deformans or osteodystrophia deformans, is a metabolic bone disease in which the body is unable to complete the normal bone growth cycle. This leads to the growth of abnormally large and weak bone.
Clinical Manifestations
Most often this disorder asymptomatic, and is therefore usually diagnosed when an x-ray or bone health monitoring lab test is taken for another purpose.
Those who are symptomatic might experience bone pain, joint pain or stiffness, pathologic fracture, hearing loss, headache, visible boney deformities such as bowed legs or enlarged head.
Red flags
Osteoporosis circumscripta is a radiographic finding of often large lytic lesions seen in the skull. Since skull involvement can lead to hearing loss, it is important to recognize that diminished hearing with increasing skull size is a hallmark of skull hypertrophy from gigantism or Paget’s disease.
Epidemiology
3-4% of the population, typically in those aged 50-60, are affected by this disease. It is more commonly found in those of northern European descent, and sometimes has a familial link. Men are more likely to be affected by this disease than women.
Pathology and pathophysiology
The abnormality found in paget’s disease is that of bone breakdown and reproduction. It begins with elevated activity and number of osteoclasts. Because of increased resportion, the body responds by increasing the production of new bone, however the bone is created weaker woven hypervascular bone.
Histologically, one will find highly disorganized bone with prominent cement lines and numerous overactive osteroclasts with many nulclei. Evidence on increased vascularity is also present.
Differential diagnosis
- Osteitis fibrosa cystica (hyperparathyroidism)
- Bone tumor, eg, osteosarcoma
- Multiple myeloma
- Metastatic cancer
- Fibrous dysplasia
- Fibrogenesis imperfecta ossium
Etiology
The two most popular theories for the cause of paget’s disease suggest viral or genetic origins. The viral origin is based on the finding of nuclear inclusion bodies within osteoclast cells and evidence of viral transcription in those with the disease.
Radiographic and laboratory findings
X-Ray evidence or elevated alkaline phosphatise is usually the first indicator is the disease. In addition to osteoporosis circumscripta one might find the blade of grass sign, in which the lytic lesion of paget’s forms a v shaped radiolucent area next to bone.
The radiographic appearance is typically that of decreased bone mineral density in one entire bone early in the disease course followed by trabecular thickening and coarsening of the bone in the later stages.
Once suspected other tests such as a bone scan (increased uptake in active lesions), alkaline phosphatase (elevated), Serum calcium (elevated), urinary hydroxproline (elevated) are useful for confirmation.
Risk factors and prevention
As there is some genetic evidence for this disease, a family member with Paget’s increased ones risk, especially if it is a first degree relative.
Once discovered bisphosphonates are useful in preventing disease complications.
Treatment options
Treatment is usually reserved for the symptomatic patient or those with lesions in dangerous areas such as the skull, which can lead to hearing loss, or weight bearing bones, where lesion can lead to fracture.
Current treatment includes bisphosphonates and calcitonin. The first is used to increase bone density, while the second is more rarely used, it can decrease the amount of calcium in the blood by decreasing absorption, and inhibit osetoclast activity.
Surgery is most often indicated to prevent fractures and for joint disease.
Outcomes
The natural history for this disease is quite slow, and complications are uncommon with early diagnosis, treatment, and monitoring. Fracture, usually of the femur, is the most common problem in these patients. Deafness, heart failure, paraplegia, or spinal stenosis are other uncommon obstacles facing those with untreated disease.
Holistic medicine
These patients typically do well. Regular follow-up is the key to preventing complications.
Key terms
osteoporosis circumscripta, osteitis deformans, osteodystrophia deformans, paget’s disease of bone, "blade of grass" lesion
Skills and competencies
A medical student should be able to identify signs and symptoms of paget’s disease, know the underlying pathophysiology, and understand the current diagnosis and treatment options.
