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DISEASES OF BONES

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BONE CELLS3 types of cells

1. Osteoblasts: bone-forming (present on surface)2. Osteocytes: mature, adult, main type (able to form &

resorb bone)

3. Osteoclasts: bone-destroying

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DEVELOPMENT & GROWTH OF BONESIntramembranous ossification (bones of the skull)

Endochondral ossification (limb bones)

E. Epiphysis PC. Proliferative Cart. HC. Hypertrophic Cart.

V. Vascular invasion CC. Calcified Cartilage

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HORMONAL CONTROL

Three main hormones regulate calcium & phosphate

metabolism:

1. Parathyroid hormone bone resorption

2. Calcitonin inhibits movement of calcium from bone

to blood

3. Vitamin D absorption of calcium from the intestines

vitamin D leads to Rickets in children &

Osteomalacia in adults

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DISORDERS OF GROWTH & MATURATION

4 different groups:1. Delayed cartilage maturation disorders Cretinism

Morquio's disease2. Bone Modeling disorders osteopetrosis

3. Epiphyseal plate disordersAchondroplasia

Scurvy

Asymmetrical cartilage growth

Kyphoscoliosis

Osteomalacia

4. Delayed Bone Maturation disorders

Osteogenesis imperfecta

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CONGENITAL BONE DISORDERS (hereditary)

1- OSTEOGENESIS IMPERFECTA (Ol)

(Brittle bone disease)

Etiology:

Hereditary disorderof collagen synthesis leading to

formation of abnormal lamellar collagen.

A minority of patients do not inherit the disorder (they

think it is due to spontaneous genetic mutation)

. Insufficient synthesis of type I collagen

. Other tissues affected: abnormal dentition

hearing loss

blue sclera

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OSTEOGENESIS IMPERFECTA (Ol)


Pathology:

Bone: decreased synthesis of collagen type I (principal

component of osteoid tissue)

reduced bone formation

thin cortex

+rarefaction of trabeculae (light, less dense)

pa pathological fractures

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Prevalence:Estimate range from 20,000 to 50,000

Treatment:

- No cure for OI

- A surgical procedure called rodding is frequently considered forindividuals with OI by inserting metal rod through the length of

long bones to strengthen them & prevent &/or correct deformity.

- Exercise as much as possible to promote muscle & bone strength.

- maintain healthy weight, nutritious diet, avoid smoking, excessivealcohol and caffeine consumption & taking steroid medications (all

of which may deplete bone & exacerbate bone fragility)Source:

http://www.osteo.org/newfile.asp?doc=i101i&doctitle=Fast+Facts+on+Osteogenesis+Imperfecta

&doctype=HTML+Fact+Sheet

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2- OSTEOPETROSIS

(Alber's Schnberg disease) or

"Marble bone disease"Hereditary abnormality of osteoclasts (rare disease)

Overgrowth and sclerosis of bones increased

density of the skeleton

Obliteration in the medullary cavity anemia

Despite the "too much" bone, it breaks easily

(pathological fractures)

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OSTEOPETROSIS

(Alber's Schnberg disease) or "Marble bone

disease"

Less bone resorption resulting in a net bone

overgrowth

Bone deformities and nerve compressionmanifestations (reduction of neural foramina, deafness)

Two patterns:

1. Malignant, become evident in-utero and infancy ,autosomal recessive

2. benign, adult, autosomal dominant

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A. X-ray (misshaped & dense bone of lower extrimities)

B. Obliteration of the bone marrow

C.Disorganization of bony trabeculae (containing core of

calcified cartilage)

A B C

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3- ACHONDROPLASIA

. Decreased cartilaginous growth

. Dwarfism

. Long bones are short and relatively thick

Epidemiology:

- It is the most common of a group of growth defects characterized by

abnormal body proportions

- Only 20% of cases have a positive family history

- 80% is thought to be due to genetic mutation

- 1 in every 20,000 live births

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3- ACHONDROPLASIA

Manifestations:

- Normal membranous ossification normal skull,

facial bones & axial skeleton

- Limbs much shorter than normal

- Narrow foramen magnum and spinal canal may

accumulation of too much fluid in brain

(hydrocephalus)- High risk of repeated middle ear infection hearing

loss

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3- ACHONDROPLASIA

Traetment:

- There is no specific treatment for achondroplasia.

- Related abnormalities, including spinal stenosis and spinal

cord compression, and hydrocephalus should be treated

when they cause problems.

Prognosis:

- Most can live normal life span with careful attention to

dangerous complications.

Prevention:

- genetic counseling

Source: http://www.nlm.nih.gov/medlineplus/ency/article/001577.htm#Treatment

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3- ACHONDROPLASIA

Dwarfism

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Dr. Ayad 18Normal growing epiphyseal plate

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Dr. Ayad 19The epiphyseal (growth) plate of an achondroplastic dwarf

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4-Osteochondroma

(Hereditary Multiple Exostosis)

Features- benign masses

Development defect in epiphyseal cartilage of long bone,

grows laterally in soft tissue

Mass formed of outer hyaline cartilage, cortex &

medullary cavity in continuity with those of long bone

Growth stops when epiphysis closes off

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Manifestations:

1. Either solitary (mostly) or multiple (inherited,

autosomal dominant)

2. Diagnosed in children (multiple) & young adults,

(solitary)

3. Men are affected 3 times more than women

4. Mushroom-shaped mass, 3-5 cm

5. Asymptomatic or symptomatic: deformity, pressure

6. Malignant change (< 1%)

S h i f h d l i

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Schematic of the development over time an

osteochondroma, beginning with an outgrowth from

the epiphyseal cartilage.

O h d d di h

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Osteochondroma, gross and radiograph

This is an osteochondroma of bone. This lesion appears as a

bony projection (exostosis). Most are solitary, incidental

lesions that may be excised if they cause local pain.

O h d Th i l f

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Osteochondroma. The cross-sectional appearance of

an osteochondroma shows the cap of calcified

cartilage overlying poorly organized cancellous bone.

O t h d i i

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Osteochondroma, microscopic

The microscopic appearance of an osteochondroma displays

the benign cartilagenous cap at the left and the bony cortex at

the right. This bone growth, though benign, can sometimescause problems of pain and irritation that leads to removal

surgically.

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