Bone Disease Manifested in Jaw

Fibro-osseous Lesions of Periodontal Origin

• Periapical cemental dysplasia
• Florid osseous dysplasia
• Cemento-ossifying fibroma
• Cementifying fibroma
• Ossifying fibroma

FIBROUS DYSPLASIA

Definition

• Confined to one bone - called monostotic fibrous dysplasia
• Involving multiple bones - called polyostotic fibrous dysplasia

• Fibrocystic disease
• Osteitis fibrosa localisata
• Focal osteitis fibrosa
• Fibro-osteodystrophy

Etiology

• FD is a genetic, non-inherited condition.
• Caused by a mutation in the gene GNAS1 on chromosome 20.
• This gene encodes the alpha subunit of the stimulatory G protein-coupled receptor (Gsα).
• The activating mutations occur post-zygotically, replacing arginine residue amino acid with either a cysteine or histidine amino acid.
• The mutation selectively inhibits GTPase activity, resulting in constitutive stimulation of AMP-protein kinase A intracellular signal transduction pathways.

Systemic manifestations of mutated Gsα protein-coupled receptor complex:

Types

1st Classification:

• Jaffe-Lichtenstein syndrome - Pigmented lesions of the skin (café au lait spots)
• McCune-Albright's syndrome - Pigmented lesions of the skin PLUS endocrine disturbances of various types

2nd Classification (according to Stewart):

Subclinical Fibrous Dysplasia

Clinical Features

Monostotic Fibrous Dysplasia

• Discovered in young patients, usually children younger than 10 years
• Affects both sexes equally

• Involves only one bone
• No extra-skeletal effects, except occasional pigmented skin lesions
• Accounts for about 80-85% of all cases
• Most frequent sites: ribs, femur, maxilla, and mandible

• Painless swelling of the bone is the most common complaint

Polyostotic Fibrous Dysplasia (Jaffe's type)

• Involves multiple bones
• Female to male ratio = 3:1 (females more commonly affected)

Also mentioned at the top of the page (preceding context):

• Aneurysmal bone cyst
• Jaw lesions in hyperparathyroidism
• Paget's diseaseHere is everything explained from the picture (Textbook of Oral Pathology, page on Fibrous Dysplasia continued):

Figure 23.1

Café au Lait Spot

• Skin lesions consisting of irregularly pigmented, light brown melanotic spots - described as "café au lait spots"
• The pigmented lesion may be congenital and pigmented oral mucosal macules may also be present
• Margins of café au lait spots are typically very irregular, resembling a map of coast line of Maine
• Recurrent bone pain is the most common presenting skeletal symptom
• Skeletal lesions may be unilateral in distribution or may involve nearly all bones of the body
• Spontaneous fracture is a common complication
• In rare cases, continuous and inexorable extension results in great deformity and blindness

Albright's Syndrome

• Shows additional endocrinal disturbances like:
  • Precocious puberty
  • Goiter
  • Hyperthyroidism
  • Hyperparathyroidism
  • Cushing's syndrome
  • Acromegaly
• Exclusively found in females
• Vaginal bleeding has been noted
• Secondary sexual characteristics such as pubic and axillary hair and development of breasts are evident by the age of 5 years
• May result in crippling deformities or fracture
• Precocious puberty is rare in boys and manifested as gynecomastia
• Long bones are frequently affected
• Bone and skin lesions in polyostotic form are unilateral
• Skeletal lesions become static with cessation of growth but proliferation may continue, particularly in the polyostotic form
• Another disorder characterized by fibrous dysplasia with intramuscular myxomas is termed Mazabraud syndrome

Oral Manifestations

Monostotic

• Maxilla is more commonly affected than mandible
• Most changes occurring in the posterior region
• Most common area involved is premolar-molar area

• There may be unilateral facial swelling, which is slow growing with intact overlying mucosa
• Swelling is usually painless but patients may feel discomfort in some cases; others complain of frank pain
• Enlarging deformities of alveolar process - mainly buccal and labial cortical plates are seen (Fig. 23.1)
• In mandible, it causes protuberant excrescence of the inferior border of the mandible
• Teeth in the affected area are either malaligned and tipped or displaced
• Dental anomalies such as supernumerary teeth have been reported in connection with monostotic fibrous dysplasia
• These supernumerary teeth often remain impacted and may affect the eruption of normal teeth

Craniofacial Fibrous Dysplasia

• If fibrous dysplasia extends to involve the maxillary sinus, zygomatic process, floor of orbit and sometimes toward the base of the skull, it is known as craniofacial fibrous dysplasia
• Results in severe malocclusion and marked facial deformity
• Craniofacial lesions may lead to:
  • Anosmia (loss of sense of smell)
  • Deafness
  • Blindness
  • Proptosis of the affected eye

Polyostotic (Jaffe's type)

• Expansion and deformities of jaws occur
• Eruption pattern of teeth is disturbed due to loss of support of developing teeth
• Asymmetry of facial bones
• Ballooning of jaws - gross enlargement and deformity
• In some cases, intraoral pigmentation can be seen

Radiological Features

Ground Glass Appearance

• Patient usually gets a ground glass appearance
• Results from superimposition of myriad of poorly calcified bone trabeculae arranged in a disorganized pattern (Fig. 23.2)

• Not well demarcated - it blends imperceptibly into the adjacent bone
• There is expansion of lingual and buccal cortical plates
• In some cases, superior displacement of inferior alveolar canal is seen
• In earlier stages, the lesion may be radiolucent or mottledHere is everything explained from the picture (Textbook of Oral Pathology, page 579 - Bone Disease Manifested in Jaw):

Figures on This Page

• Figure 23.2 - Fibrous dysplasia showing ground glass appearance of the lesion (X-ray image)
• Figure 23.3 - Chinese letter pattern bony trabeculae seen in fibrous dysplasia (histopathology image)
• Figure 23.4 - Fibrous dysplasia showing irregularly shaped trabeculae of woven bone in fibrous stroma (histopathology image)

Maxillary Sinus Involvement

• In case of involvement of maxilla, the lesion may cause:
  • Displacement of sinus floor superiorly
  • Obliteration of maxillary sinus can occur

Laboratory Examination

• Serum calcium and serum phosphorus concentration - usually within normal limits
• Serum alkaline phosphatase activity - usually within normal limits
• BUT in rare instances, particularly when the polyostotic lesions are numerous and active, the serum alkaline phosphatase levels may be elevated in 50% of the cases

Histopathological Features

Monostotic Fibrous Dysplasia

• The lesion is essentially a fibrous bone made up of proliferating fibroblast in a compact stroma of interlacing collagen fibers
• Irregular trabeculae of bone are scattered throughout the lesion, with no definite pattern of arrangement
• Some of these trabeculae are C-shaped and described as Chinese character shaped (Fig. 23.3)
• These trabeculae are usually woven bone, but may be lamellar in some cases
• With progressive maturation, fibrous dysplasia of jaws undergoes maturation to a lesion consisting of lamellar bone in a moderately cellular connective tissue stroma
• The bony trabeculae in these mature lesions tend to run parallel to one another (Figs 23.4 and 23.5)

Polyostotic Fibrous Dysplasia

• The lesions are composed of fibrillar connective tissue within which are numerous trabeculae of coarse, woven bone
• Trabeculae are irregular in shape but evenly spaced, showing no relation to functional pattern
• The osteocytes are quite large and collagen fibers of these trabeculae can often be seen into the fibrous tissue
• These trabeculae have typically wide osteoid seams
• Osteoclastic activity may be seen where the calcification of osteoid extends to the surface of the trabeculae

Management

• Surgical removal of the lesion should be carried out if necessary

Summary Table of Key Points