Paget Disease of Bone and Metabolic Bone Disorders

Paget disease of bone, historically called osteitis deformans, is a focal disorder of bone remodelling in which the normal, orderly turnover of bone is replaced by greatly accelerated and disorganized resorption and formation. The result is bone that is enlarged, structurally weak, and abnormally shaped. When the disease involves the maxilla or mandible it produces characteristic enlargement of the jaws, and it stands here as the principal example of a metabolic bone disorder that manifests in the maxillofacial skeleton.

Definition

Paget disease of bone is a chronic disorder of focally increased and disorganized bone remodelling, in which excessive osteoclastic resorption is followed by exuberant but architecturally abnormal bone formation, producing enlarged, weakened bone that may involve the jaws among other sites.

Scope

This entry describes Paget disease as a representative metabolic bone disorder affecting the jaws: its underlying disturbance of bone remodelling, its genetic and possibly viral contributions, and its maxillofacial manifestations. It is a reference and educational account of the disease as a concept and does not provide diagnostic criteria or treatment recommendations for individuals.

Core questions

• What goes wrong in bone remodelling to produce the enlarged, disorganized bone of Paget disease?
• What genetic and environmental factors are thought to contribute to its pathogenesis?
• How does Paget disease present when it involves the maxilla or mandible?

Key concepts

• Disordered bone remodelling
• Excessive osteoclastic resorption
• SQSTM1 (p62) gene mutations
• Possible paramyxovirus involvement
• Mosaic (jigsaw) bone pattern
• Jaw enlargement (leontiasis ossea)

Mechanisms

The core abnormality in Paget disease is a focal dysregulation of bone remodelling in which osteoclasts are abnormally large, numerous, and overactive, producing intense bone resorption that is followed by rapid, compensatory but disorganized bone formation. The resulting bone has a characteristic disordered, mosaic architecture and is mechanically weak despite being enlarged (Ralston, 2012). Pagetic osteoclasts show distinctive features, and the disease has a strong genetic component, with mutations in the SQSTM1 gene (encoding p62) found in many familial and some sporadic cases; an additional environmental contribution, possibly involving paramyxovirus infection of osteoclasts, has been proposed but remains debated (Ralston, 2012). When the process involves the jaws, the accelerated remodelling produces progressive bony enlargement, alteration of the bite, and radiographic changes; the dental literature has long noted these maxillofacial manifestations (Smith & Eveson, 1981).

Clinical relevance

Paget disease is the metabolic bone disorder most often discussed in oral pathology because its jaw involvement produces distinctive enlargement and radiographic change, and because the altered bone behaves differently from normal bone during dental procedures. This entry presents the disease as a reference topic — describing its biology and manifestations — and is not a basis for individual diagnosis or management decisions.

Epidemiology

Paget disease is predominantly a condition of older adults and is uncommon before middle age. It shows striking geographic variation, having been most frequent in populations of British and Western European descent, and its prevalence has been reported to be declining in several regions over recent decades. The skull and jaws are among the sites that may be involved, though the axial skeleton and long bones are more commonly affected.

Debates

Is there a viral contribution to the pathogenesis of Paget disease?

A paramyxovirus infection of osteoclasts has been proposed as an environmental trigger acting alongside SQSTM1 and other genetic factors, but direct and reproducible evidence for a viral cause remains contested.

Key figures

• James Paget
• Stuart Ralston

Seminal works

• ralston-2012
• langston-2010

Frequently asked questions

Why is bone enlarged but weak in Paget disease?

Remodelling is greatly accelerated but disordered: intense osteoclastic resorption is followed by rapid, architecturally chaotic bone formation, so the bone becomes larger yet structurally abnormal and mechanically weak.

How does Paget disease affect the jaws?

When it involves the maxilla or mandible, the accelerated, disorganized remodelling causes progressive enlargement of the jaw with altered occlusion and characteristic radiographic changes.