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Flashcards in Bone Deck (24):


Impaired cartilage proliferation in the growth plate leading to short stature or DWARFISM due to ACTIVATING MUTATION of fibroblast growth factor receptro FGFR3. Over expression of FGFR3 inhibits growth.
Clinically see short extremities with normal sized head and chest due to poor endochondrial bone formation (how long bones grow)


Endochondral vs Intramembranous Bone Formation

Endochondral = formation of a cartilage MATRIX which is then replaced by bone. Mechanism of LONG BONE growth

Intramembranous = formation of bone WITHOUT preexisting cartilage MATRIX. Way FLAT bones grow (skull and rib cage)


Osteogenesis Imperfecta

Congenital defect in bone formation from auto dominant defect in Collagen Type bONE synthesis.
Get weak bone that fractures easily, if middle ear bones fracture get hearing loss, and thinning of scleral collagen reveals underlying CHOROIDAL VEINS which leads to BLUE SCLERA



Inherited defect of osteoclast/bone resorption resulting in abnormally thick heavy bones that fracture easily.
Usually see carbonic anhydrase II mutation leading to lack of acidic environement needed for bone resorption.
Clinically see
1) Bone fractures
2) Anemia, thrombocytopenia, and leukopenia with extramedullary hematopoiesis (bony replacement of marrow (myelophthisic process)
4) hydrocephalus if foramen magnum is narrowed
5) Renal tubular acidosis = lack of carbonic anhydrase II results in impaired ability to makde bicarb leading to a metabolic acidosis
Treat with BONE MARROW TRANSPLANT since osteoclasts are derived from monocytes


Vitamin D

Derived from sunlight and diet
Activation requires 25-hydroxylation by the liver followed by 1-alpha-hydroxylation by proximal tubule cells of the kidney
Raises serum calcium and phosphate by
1)increasing absorption in intestine
2) Increasing reabsorption in kidney
3) increasing resorption of bone

Deficiency seen in poor diet, malabsorption, and kidney and liver failure



Defective mineralization of OSTEOID (layed down by osteoblasts then mineralized with calcium and phosphate to form bone)
Due to low vitamin D in children.
Clinically see:
1) Pigeon breast deformity = inward bending of the ribs with anterior protrusion of the sternum
2) Frontal bossing/enlarge forehead = osteoid deposition in skull
3) Rachitic rosary = osteoid deposition in costochondral juntion
4) Bowing of the legs



Low vitamin D in adults.
Inadequate mineralization results in weak bone with increased risk for fracture.
Labs show:
Decreased serum calcium and phosphate
increased PTH
Increased alkaline phosphatase



Reduction in trabecular bone mass that results in porous bone with increased risk of fracture
Peak bone mass is achieved at 30 and based on genetics, diet and exercise. Thereafter bone mass is lost. Lost more quickly when dont exercise, poor diet, and loss of estrogen
Clinically see: Bone pain and fractures in weight bearing areas such as vertebrae (shrinking and kyphosis), hi p and distal radius
Labs = serum calcium, phosphate, PTH and alkaline phosphatase are normal
Treatment (1) exercise, vitamin D, and calcium (2) Bisphosphonates = induce apoptosis of osteoclasts (3) estrogen replacemnt in theory (increases cancer) (4) NOT glucocorticoids


Paget Disease of Bone

Imbalance between osteoclasts and osteoblasts function, generaly in adults above 60.
May have viral etiology
Localized process involving one or more bones NOT entire skeleton
Distinct stages are 1)osteoclastic= osteoclasts break down bone independently of PTH and osteoblasts directions 2) mixed osteoblastic and ostecolastic = osteoclastic eventually burn out leading to 3)osteoblastic
Get thick sclerotic boens that fracture easily and have mosaic pattern of lamellar bone
Clinically see: bone pain, increasing hat size, hearing loss, lion like facies, isolated elevated alkaline phosphatase
Treatment = calcitonin (inhibits osteoclasts fxn) or bisphosphonates (induce apoptosis of osteoclasts)
Complications include high output cardiac failure (formation of AV shunts in bone) and osteosarcoma



Infections of marrow and bone (more common in CHILDREN)
Transient bacteremia (children) seeds metaphysis while open wound bacteremia (adults) seeds epiphysis
1) Staph aureus = most common
2) n gonorrhoeae = sexually active
3) salmonella = SICKLE CELL DISEASE
4) Pseudomonas = DIABETICS or IV users
5) Pasteurella = cat/dog bite/scratch
6)myobacterium = involves vertebrae(potts disease)
Clinically get bone pain with systemic signs of fever and leukocystosis. See lytic focus surrounded by sclerosis on x-ray


Avascular Aseptic Necrosis

Ischemic necrosis of bone and bone marrow
Causes include trauma or fracture (most common), steroids, SICKLE CELL ANEMIA, and caisson disease (gas emboli like nitrogen precipitates out of blood and into the bone)
Osteoarthritis and fracture are major complications



Benign tumor of bonethat most commonly arises on surface of facial bones
associated with Gardner Syndrome (familail adenomatous polyposis, fibromatosis in retroperitoneum, osteoma of facial bone)


Osteoid Osteoma

Benign tumor of osteoblasts (that produce osteoid) surrounded by a rim of reactive bone.
See in young adults and more commonly in males
Arises in CORTEX of LONG BONES (femur)
Presents as bone pain that RESOLVES with aspirin
bony mass <2cm with a radioluscent core (osteoid)



Similar to osteoid osteoma but is GREATER than 2cm, arises in vertebrae, and NOT respond to aspirin



Tumor of bone with an overlying cartilage cap that arises a lateral projection of the growth plate (metaphysis).
Overlying cartilage can transform rarely to chondrosarcoma



Malignant proliferation of osteoblasts
Peak incidence is teenagers (espeically if have familial retinoblastoma) and also in elderly (with paget disease or radiation exposure)
Arises in METAPHYSIS of LONG BONES, usually in distal femur or proximal tibia
Presents as pathologic fracture or bone pain with swelling
On x-ray will see a destructive mass with "SUNBURST" appearing and lifting of the periosteum called "CODMAN TRIANGLE"
Biopsy shows pleomorphic eclls that produce osteoid


Giant Cell Tumor

Tumor of multinucleated giant cells and stromal cells
youn agults
arises on EPIPHYSIS of long bones, usually in the distal femur or proximal tibia
"SOAP BUBBLE" appearance on x-ray
Locally aggressive tumor that may recur


Ewing Sarcoma

Malignant proliferation of poorly differentiated cells derived from NEUROECTODERM
Arises in DIAPHYSIS of long bones, usually in male children appearance on x-ray
Biopsy finds small round blue cells that resemble lymphocytes
easily confused with lymphoma or chronic osteomyelitis
often presents with mets that are responsive to chemo


Chondroma vs Chondrosarcoma

Chondroma = BENIGN tumor or cartilage, arises in MEDULLA of SMALL bones of HANDS and FEET

Chondrosarcoma = MALIGNANT tumor of cartilage in MEDULLA of PELVIS or CENTRAL SKELETON


Metastatic Bone Tumors

More common than primary tumors
Results in osteolytic (punched out) lesions
Prostatic carcinoma classically produces osteoblastic lesions



Benign tumor of adipose tissue
most common benign soft tissue tumor in ADULTS



Malignant tumor of adipose tissue
Most common malignant soft tissue tumor in ADULTS
LIPOBLAST is characteristic cell



BEnign tumor of skeletal muscle
cardiac rhabdomyoma is associated with tuberous sclerosis



Malignant tumor of skeletal muscle
Most common malignant soft tissue tumor in CHILDREN
RHABDOMYOBLAST is characteristic cell and it is DESMIN +
Most common site is HEAD and NECK. But on boards CLASSIC site is VAGINA of YOUNG GIRLS