Osteodystrophies of Oro-maxillo facial Region Clinical Features, Radiological Features, Histological Features and Management

Osteodystrophies definition
Osteodystrophies are disorders of bone other than neoplastic and inflammatory conditions.

Classification of osteodystrophies in OMF region
1.       Fibro cement osseous lesions
2.       Giant cell lesions
3.      Inherited and developmental disorders of bone
4.       Metabolic disorders of bone
5.       Miscellaneous

Fibro cement osseous lesions-Classification

A.Developmental
·         Mono ostotic fibrous dysplasia
·         Polyostatic Fibrous dysplasia
·         Polyostatic fibrous dysplasia with endocrinopathy (Macune Albright’s syndrome)
·         Polyostatic fibrous dysplasia with pigmentation (Jaffe-Lichtenstein syndrome)
·         Polyostatic fibrous dysplasia with myxomas
·         Craniofacial fibrous dysplasia

B.Reactive lesions
·         Hereditary
o   Familaial gigantiform cementoma
·         Non Hereditary
o   Periapical cemento osseous dysplasia
o   Florid cement osseous dysplasia
o   Focal cemento osseous dysplasia

C.Neoplastic
·         Conventional cemento ossifying fibroma
·         Juvenile aggressive cement ossifying fibroma

Fibro osseous lesions
One in which bone is replaced by cellular fibrous tissue which gradually matures with the formation of woven bone, lamellar bone ,or very dense amorphous mineralization.

Diagnosis of fibrocemento osseous lesions
The diagnoses of fibrocemento osseous lesions are done using clinical, radiological and histopathological correlation, not by features in isolation.

Fibrous Dysplasia
A benign self limiting but unencapsulated lesion, normally occurring in young subjects. Fibrous dysplasia clinically presents as a painless swelling of the bone involved. Usually, fibrous dysplasia is a self-limiting disease. Therefore, treatment is only required if there are problems due to local increase in size of the affected bone. Sometimes, an osteosarcoma may arise in fibrous dysplasia.
  • Caused by mutation in the GNAS-1 gene
  • Mutation is not inherited but somatic
  • Mutation of gene in causing different types of fibrous dysplasia depending on the time of mutation.
  • If gene is mutated very early embryonic life (undifferentiated stem cells) it affects osteoblasts, melanocytes and endocrine cells),many affected daughter cells are present in different organs and Albright’s syndrome results.
  • If gene is mutated in later stages (after migration and differentiation of skeletal progenitor cells), it affects multiple bones causing polyostatic fibrous dysplasia.
  • Onset 1st and 2nd decades of life
  • Commonly occurring in maxilla and adjacent bones

Albright’s syndrome
Is a combination of
1.       Polyostotic fibrous dysplasia
2.       Cutaneous pigmentation
3.       Endocrine abnormalities (diabetes mellitus ,precocious puberty)
4.       Premature skeletal maturation

Radiology
The classical appearance is described as orange-skin or groundglass radiopacity without defined borders.
Initially appear as well defined radiolucency, later with indistinct margins. Fine trabeculation forming “Ground Glass” appearance as lesion develops. Jaw swelling with thinning of original cortex.


Monostotic fibrous dysplasia
  • Commener than polyostotic form
  • Give rise to a bony swelling caused by a poorly circumscribed area of fibro osseous proliferation
  • Starts in childhood-undergoes arrest in early childhood
  • Jaws are common sites-when the jaws are involved,a painless,smoothy rounded swelling usually of the maxilla is typical
  • When the mass become large malocclusion occur
  • Lesions affecting the maxilla may spread to involve contiguous skull bones causing deformity of the orbit ,base of  the skull and cranial nerve lesions
  • Radiologically-normal bone trabecullation replaced by ground glass or orange peel pattern.
  • Lesions merge imperceptibly with normal bone at margins

Histopathology

In the jaws, fibrous dysplasia may consist of both woven and lamellar bone, as shown in this photomicrograph taken with the use of partly polarised light to enhance the collagenous scaffold of the bone.

  • Vary with age of the lesion
  • Loose fibrous tissue(Whorled, fascicular,random)
  • The normal bone replaced by fibrous connective tissue containing slender trabecullae of bone
  • Early lesions bony trabeculae do not join each other
  • Trabeculae of bone in the cellular areas show a “Chinese letter appearance”
  • Osteoblasts are scattered throughout the substance of the trabecullar rather than surrounding them
  • Older lesions lamellar maturation reversal lines and parallel arrangement of bony trabeculae(onion skin appearance)
  • Usually becomes inactive with skeletal  maturation


Polypstotic fibrous dysplasia
·         Females>males
·         Histologically and radiologically indistinguishable from monostotic form

Management
Disease is self limiting. Grossly disfiguring lesions need to be excised(Contouring,resectiona dn reconstruction) . This should be delayed if possible until the process become inactive. Small risk of sarcomatous changes in poly ostotic type.

Osseous Dysplasia
Osseous dysplasia is a pathologic process of unknown aetiology located in the tooth-bearing jaw areas in the vicinity of the tooth apices and is thought to arise from the proliferation of periodontal ligament fibroblasts that may deposit bone as well as cementum. The condition occurs in various clinical forms that bear different names. However, all have the same histomorphology: cellular fibrous tissue, trabeculae of woven as well as lamellar bone and spherules of cementum-like material. The ratio of fibrous tissue to mineralized material may vary and it has been shown that these lesions are initially fibroblastic, but over the course of several years may show increasing degrees of calcification. This variation in ratio of soft tissue to hard tissue is reflected in the radiographic appearance; lesions are predominantly radiolucent, predominantly radiodense or mixed.
Osseous dysplasia lacks encapsulation or demarcation,but tends to merge with the adjacent cortical or medullary bone. The several subtypes of osseous dysplasia are distinguished by clinical and radiological features.

Periapical osseous dysplasia occurs in the anterior mandible and involves only a few adjacent teeth.
A similar limited lesion occurring in a posterior jaw quadrant is known as Focal osseous dysplasia.


Florid osseous dysplasia is non-expansile, involves two or more jaw quadrants and occurs in middle-aged black females.


Familial gigantiform cementoma is expansile, involves multiple quadrants and occurs at a young age. This type of osseous dysplasia shows an autosomal dominant inheritance with variable expression, but sporadic cases without a history of familial involvement have also been reported. Simple bone cysts may be seen with florid and focal osseous dysplasia. Osseous dysplasia has to be distinguished from ossifying
fibroma. Osseous dysplasia is a mixed radiolucent- radiodense lesion with ill-defined borders in the tooth-bearing part of the jaws, either localised or occupying large jaw areas depending on the type. In contrast, ossifying fibroma is usually a localised lesion that expands the jaw, and is predominantly radiolucent with radiodense areas. Osseous dysplasia also has to be differentiated from sclerosing osteomyelitis. Sclerotic lamellar bone trabeculae and well-vascularised fibrous tissue with lymphocytes and plasma cells define sclerosing osteomyelitis,
Whereas cementum-like areas and fibrocellular soft tissue are lacking. The various forms of osseous dysplasia do not require treatment unless necessitated by complications such as
Infection of sclerotic bone masses, as may occur in florid osseous dysplasia, or facial deformity, as may be seen in familial gigantiform cementoma.

Management
Management of focal cemental dysplasia is usually difficult because surgical removal resulting in small hemorrhagic gritty fragments.

Cemento ossifying fibroma
Ossifying fibroma , formerly also called cemento-ossifying fibroma is a well-demarcated lesion composed of fibrocellular tissue and mineralised material of varying appearance. It occurs most often in the 2nd through the 4th decades. The lesion shows a predilection for females, is mostly seen in the posterior mandible and may occur multifocally. Chromosomal abnormalities have been observed in ossifying fibromas. Data are still too scarce to determine their pathogenetic significance.
Ossifying fibroma contains both cell-rich and cell-poor areas as well as well-structured bone and amorphous calcifi ed material

Ossifying fibroma may also contain more smoothly contoured bony elements, formerly thought to represent cementum
 Juvenile trabecular ossifying fi broma shows slender bony trabeculae rimmed with osteoblasts that merge with an extremely cellular stroma
At higher magnification, the plump osteoblasts that line the bony trabeculae in juvenile trabecular ossifying fi broma are shown to be a prominent feature

Ossifying fibroma is composed of fibrous tissue that may vary in cellularity from areas with closely packed cells displaying mitotic figures to almost acellular sclerosing parts within one and the same lesion. The mineralized component may consist of plexiform bone, lamellar bone and acellular mineralised material, sometimes all occurring together in one single lesion. Juvenile psammomatoid and juvenile trabecular ossifying fibroma are subtypes. Juvenile trabecular ossifying fibroma consists of cell-rich fibrous tissue with bands of cellular osteoid together with slender trabeculae of plexiform bone lined by a dense rim of enlarged osteoblasts. Sometimes these trabeculae may anastomose to form a lattice. Mitoses are present, especially in the cell-rich areas. Also, multinucleated giant cells, pseudocystic stromal degeneration and haemorrhages may be present. Due to its cellularity and mitotic activity, the lesion may be confused with osteosarcoma. However, atypical cellular features or abnormal mitotic figures are not seen.
Moreover, the lesion is demarcated from its surroundings. Juvenile psammomatoid ossifying fibroma is characterized by a fibroblastic stroma containing small ossicles resembling psammoma bodies, hence its name. The stroma varies from loose and fibroblastic to intensely cellular. The spherical or curved ossicles are acellular or include sparsely distributed cells. They should not be confused with the cementum-like deposits that are present in conventional ossifying fibroma. These particles have a smooth contour whereas the ossicles in juvenile psammomatoid ossifying fibroma has a peripheral radiating fringe of collagen fibres. Ossicles may coalesce to form trabeculae. Sometimes, juvenile psammomatoid ossifying fibroma contains basophilic, concentrically lamellated particles, as well as irregular thread-like or thorn-like calcified strands in a hyalinised background. Other features such as trabeculae of woven bone as well as lamellar bone, pseudocystic stromal degeneration and haemorrhages resulting
  • Benign neoplasms of the bone
  • Arising exclusively in the jaws,facial bones and skull
  • Typically causes a painless swlling in the mandibular premolar and molar region
  • Females>males
  • Fibro osseoue lesion
  • Has similarities to fibro osseous dysplasia
  • Radiographycally-starts as small radiolucency and expands slowly
  • Calcification develops centrally as the lesion enlarges
  • Most become densely calcified
  • The lesion has a sharply defined margin often within radiolucent rim surrounded by a narrow zone of cortication

Microscopy
  • Well demarcated from surrounding bone
  • Appearances are widely variable degrees of cellularity and scanty calcifications to densely calcified nodules with little stroma
  • The types of calcification

    1. trabecullae of woven bone with osteoblastic rimming
    2. dystrophic calcifications
    3. rounded calcificatons resembling cemmentricles
    4. calcifications grow gradually,fuse and ultimately from a dense mass

histologically indistinguishable from fibrous dysplasia

Juvenile aggressive cemento ossifying fibroma
  • Commener in children
  • The loose fibroblastic stroma contains very fine,lace like trabeculae of immature osteoid entrapping plum osteoblasts
  • Focal collection of  giant cells are common
  • Histological appearance similar to osteoblastoma  or osteosarcoma
  • Radiological features can avoid this misdiagnosis


Benign cementoblastoma
Benign neoplasm of cementum forming cells. The spherical masses of cemntum usually attach to tooth apex.
·         Patients mostly under 25 years
·         Lesion usually attached to apex of mandibular molar or premolar.

Histopathology
·         Dense bulbosity around tooth apex and is encapsulated
·         Mass of mineralized cementum like tissue with numerous resting and reversal lines.
·         Numerous small vascular spaces throughout the mass
·         Partial resorption of the root apex
·         Peripheral cellular zone unmineralized “Cementoid”.

Giant cell lesions

True giant cell lesions
·         Central giant cell granuloma
·         Peripheral giant cell granuloma
·         Broen tumor of hyperparathyroidism
·         Giant cell tumour
·         Cherubism

Lesions that may contain giant cells
·         Paget’s disease
·         Fibrous dysplasia
·         Aneurismal bone cyst

Central giant cell granuloma
  • Benign hyperplastic lesion of unknown aetiology
  • More common in young females over a wide age range
  • Very expensile and may be destructive may penetrate cortical bone and periosteum
  • Solid but appear as unilocular or multilocular cyst like radiolucency
  • Forms in alvelor ridge,anterior to 6s more fequently in the mandible but often in the maxilla
  • No changes in the blood chemistry
  • Treated by curettage
  • Lobulated mass of proliferating vascular connective tissue packed with giant cells

Cherubism
  • Inherited as autosomal dominant triat
  • Jaw swellings appear in infancy
  • Angle regions of mandible affected symmetrically giving typical chubby face
  • Symmetrical involvelment of maxillae also in ore severe cases
  • Radiolographycally lesions appear as multilocular cyst like areas
  • Histologically lesions consist of giant cells in vascular connective tissue
  • Lesions regress with skeletal maturation and normal facial contour restored

Paget’s Disease
Paget’s disease (osteitis deformans) is a common condition affecting particularly the skull, pelvis, vertebral column and femur in people over 40 years of age. The cause is not yet certain, but the presence in many cases of paramyxovirus-like structures seen within osteoclasts has prompted the suggestion that Paget’s disease may be of viral aetiology and the measles virus and canine distemper viruses have been under scrutiny as candidates. The pathological change is one of active bone formation proceeding alongside active bone destruction.
The affected bones are enlarged, porous and deformed. Microscopically, bone formation is seen in
trabeculae of bone with a lining of numerous osteoblasts. A mosaic appearance is formed by the frequent successive deposition of bone, cessation of deposition resulting in thin, blue “cement lines”, followed again by resumption of deposition and its cessation, and so production of further cement lines. Bone destruction is shown by the presence of numerous, large osteoclastic giant cells with Howship’s lacunae. Areas of chronic inflammatory exudate intermixed with the bone are common.
In the temporal bone the petrous apex, the mastoid and the bony part of the Eustachian tube are most frequently affected. The periosteal part of the bony labyrinth is the first to undergo pagetoid changes and the pagetoid changes spread through the bone towards the membranous labyrinth, usually with a sharp line of demarcation between the pagetoid area and the normal bony labyrinth.
 Osteogenisis imperfecta
Osteogenesis imperfecta is a general bone disease with a triad of clinical features: multiple fractures, blue sclera and conductive hearing loss. There is a congenital recessive form in newborns that is often rapidly fatal and a tardive one in adults that is inherited as a mendelian dominant and is more benign. Mutations of type I collagen genes have been established as the underlying cause leading to a general disturbance in the development of collagen, hence the thin sclerae appearing blue as well as poorly formed bone tissue. In the long bones the resorption of cartilage in the development of bone is normal, but the bony trabeculae themselves are poorly formed and the same may be seen in the temporal bone. The ossicles in the tardive form are very thin and subject to fractures. The stapes footplate is also frequently fixed. The disturbance in lamellar bone formation can lead to extreme thinness, dehiscence, and non-union of the stapedial superstructure with the footplate, or thickening with fixation of the footplate. The nature of the bony tissue causing this fixation is problematical. It has been suggested that osteogenesis imperfecta can be associated with otosclerosis so that the fixation is indeed otosclerotic. Otosclerosis, like osteogenesis imperfecta, may indeed be part of a general connective tissue disturbance. Indeed, some cases of clinical otosclerosis may be related to mutations within the COL1A1 gene that are similar to those found in mild forms of osteogenesis imperfecta.
Osteopetrosis
Osteopetrosis (often known as marble bone disease) is a rare disease of bone, in which there is a failure to absorb calcified cartilage and primitive bone due to deficient activity of osteoclasts. A relatively benign form, inherited as a dominant, presents in adults, and a malignant one, inherited as a recessive, in infants and young children. The patients with the benign form often survive to old age and present prominent ontological symptoms. The intermediate, endochondral portion of the otic capsule is swollen and appears as an exaggeratedly thickened form of the normal state. Globuli ossei composed of groups of calcified cartilage cells are normally present in this region, and in osteopetrosis they are greatly increased in number and are arranged into a markedly thickened zone. The periosteal bone is normal. The ossicles are of foetal shape and filled with unabsorbed, calcified cartilage. The canals for the seventh seventh and eighth cranial nerves are greatly narrowed by the expanded cartilaginous and bony tissue and these changes are probably responsible for the characteristic symptoms of facial palsy and hearing loss respectively.
Cleidocranial Dysplasia
Transmitted by autosomal dominant triat. Defect in CBFA-1 (Nuclear protein). Defective formation of clavicles, delayed closure of frontanells,sometimes retrusive mandible. Partial or complete loss of clavicles allow patient to bring shoulder’s together in front of the chest.not only membranous bones but all part of the skeleton is affected.
Radiological features
·         Aplasia or hypoplasia of claicles
·         Skull shows
o   Delayed closure of frontanells
o   Open skull sutures
o   Sunken sagittal suture-sagittal suture
o   Frontal and occipital bossing
o   Widened cranium-
·         Jaws shows
o   Underdeveloped maxilla-maxillary micrognathia
o   Multiple supernumerary teeth-anterior to permanent molars
o   Unerupted or delayed eruption of permanent teeth
o   Prolonged retention of primary teeth
o   Mandibular prognathism-normal in size
o   Sometimes multiple dentigerous cysts.

Achondroplasia
·         Most common type of genetic skeletal disorders
·         Manifest as short limb dawfism
·         Failure of normal cartilage proliferation in the epiphysis and base of the skull
·         Normal intelligence.CNS not affected.

Hyperparathyroidism
·         Two types
·         Primary and secondary hyperparathyroidism
·         Predominantly in middle aged females
·         Excessive parathomone secreting adenomas
·         Present with generalized osteoclastic activity with fibrosis of marrow
·         In addition, focal areas of bone resorption result in brown tumour formation.
·         Usually present with giant cell epulis and cystic lesions.

Management
Surgical removal of adenoma and subtototal excision of hyperplasia

Rickets and osteomalacia
·         Due to deficiency or resistance to Vitamin D
·         Present with reduced bone density and failure of bone mineralaization.

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