Bone Flashcards
Cause of achondroplasia
Activating mutation in fibroblast growth receptor 3 (FGFR3); AD
FGF3 inhibits growth, becomes over-expressed
Achondroplasia - clinical features, what is not affected
Short extremities, normal sized head and chest
Mental function, fertility and life span are not affected
Achondroplasia - what type of bone formation is affected
Endochondral bone formation: characterized by the formation of a cartilage matrix that is replaced with bone
ex/ long bones
vs. intramembranous bone formation: bone formed without a preexisting cartilage matrix
ex/ flat bones (skull and rib cage)
OI: what type of defect
Autosomal dominant defect in collagen type I synthesis
OI: clinical features
Multiple fractures, blue sclera (scleral collagen thins revealing underlying choroidal veins), hearing loss
Osteopetrosis is due to poor…
osteoclast function
Important genetic variant for osteopetrosis
Carbonic anhydrase II mutation -> loss of acidic environment necessary for bone resorption
Clinical features of osteopetrosis (5)
- Bone fractures
- Anemia, thrombocytopenia, and leukopenia with extramedullary hematopoiesis
- Vision and hearing impairment (impingement on CN)
- Hydrocephalus (narrowing of foramen magnum)
- Renal tubular acidosis - seen with CAII mutation, lack of CA results in decreased tubular reabsorption of HCO3- leading to metabolic acidosis
Treatment of osteopetrosis
Bone marrow transplant (osteoclasts are derived from monocytes)
Rickets/Osteomalacia is due to…
defective mineralization of osteoid (due to low Vitamin D). Osteoblasts normally produce osteoid which is then mineralized with calcium and phosphate to form bone.
Rickets most commonly arises before age 1 and presents with what four deformities?
Pigeon breast deformity
Rachitic rosary
Bowing of the legs (seen in ambulating children)
Frontal bossing (enlarlged forehead due to osteoid deposition on the skull)
Laboratory findings: Osteomalacia
Low Ca++, Phosphate
High PTH
High Alkaline phosphatase
Osteoporosis shows a reduction in which type of bone?
Trabecular (cancellous or spongy)
What factors influence peak bone mass? What causes bone mass to be lost more quickly?
Diet, exercise and genetics attribute to peak bone mass
Lack of weight bearing exercise (space travel), poor diet and decreased estrogen (menopause)can cause bone mass to be lost more quickly
Laboratory findings: Osteoporosis
Calcium, phosphate, PTH and alkaline phosphatase are all normal!
What causes Paget’s disease? At what age is this usually seen?
Imbalance between osteoclast and osteoblast function (localized - does not involve the entire skeleton)
Etiology unknown - possibly viral
>60 years
Paget disease biopsy will show…
Mosaic pattern of lamellar bone
Clinical features of Paget disease of bone (5)
Increased hat size Bone pain (micro fractures) Hearing loss (impingement on cranial nerve) Lion-like facies (craniofacial bones) Isolated elevated alkaline phosphatase
Complications of Paget disease
High-output cardiac failure - due to formation of AV shunts in bone
Osteosarcoma (osteoblasts become mutated)
Where does the bacteria seed in osteomyelitis in adults vs. kids?
Adults - Epiphysis
Kids - Metaphysis
6 common causes of osteomyelitis and what they are associated with -
Staph aureus - most common cause (90% of cases)
N gonorrhoeae - sexually active young adults
Salmonella - sickle cell disease
Pseudomonas - diabetics or IV drug users
Pasteurella - associated with dog or cat bite/scratches
Mycobacterium tuberculosis - usually involves the vertebrae (Pott disease)
Clinical features of osteomyelitis (sequestrum vs. involucrum)
Bone pain with systemic signs of infection (fever, leukocytosis) Lytic focus (abscess - sequestrum) surrounded by sclerosis (involucrum) of bone on x-ray
What is the most common benign soft tissue tumor in adults? In children?
Lipoma (benign tumor of adipose tissue)
Rhabdomyosarcoma (rhabdomyoblast is characteristic cell, desmin positive, most common sites include head/neck/vagina)
What is cardiac rhabdomyoma associated with?
Tuberous sclerosis (rare genetic disease that causes benign tumor growth in the brain and other vital organs)
Most common malignant soft tissue tumor in adults?
Liposarcoma (lipoblast is characteristic cell - adipose precursor cell)
Metastatic bone tumors are more common than primary. What type of lesion do they produce?
Osteolytic (punched out) lesions
Exception - prostatic carcinoma classically produces osteoblastic lesions
Chondroma vs. Chondrosarcoma (location)
Chondroma is a benign tumor of the cartilage. It usually arises in the medulla of small bones of the hands and feet
Chondrosarcoma is a malignant cartilage-forming tumor. Usually arises in the medulla of the pelvis or central skeleton
Osteoma most commonly arises where? Associated with what?
Benign tumor of bone
Surface of facial bones
Associated with Gardner syndrome (multiple benign tumors and colon polyps)
What is an osteoid osteoma? Who does it most commonly occur in? Where? What does it present as?
Benign tumor or osteoblasts (produce osteoid) surrounded by a rim of reactive bone
Occurs in young adults (<25 ), more common in males
Arises in the cortex of long bones (femur)
Presents as bone pain that resolves with aspirin
How is an osteoblastoma different from and osteoid osteoma?
Osteoblastomas are similar but larger (>2cm), arise in the vertebrae and present as bone pain that does not respond to aspirin
Osteochondroma: What is it, from where, what can it transform to?
A tumor of the bone with a cartilaginous cap
Arises from a lateral projection of the growth plate (metaphysics); bone is continuous with the marrow space
Overlying cartilage can transform (rarely) to chondrosarcoma
What is the most common benign tumor of bone?
Osteochondroma
Osteosarcoma - Proliferation of what? Most common in what age group? Arises where? How does it present?
Malignant proliferation of osteoblasts
Peak incidence in teenagers (bimodal, also seen in elderly)
Arises in metaphysics of long bones (usually distal femur or proximal tibia - around the knee)
Presents as a pathological fracture (tumor weakens the bone) or bone pain with swelling
Imaging sign seen with osteosarcoma
Biopsy
Destructive mass with a ‘sunburst’ appearance and lifting of the periosteum (Codman triangle)
Biopsy shows pleomorphic cells that produce osteoid (pink)
Risk factors for osteosarcoma
Familial retinoblastoma, Paget disease, radiation exposure
Giant cell tumor (what is it, what age, where does it arise, prognosis, appearance on x-ray)
Tumor comprised of multinucleated giant cells and stromal cells
Occurs in young adults
Arises in the epiphysis of long bones (distal femur or proximal tibia - knee)
Locally aggressive, may recur
Soap bubble appearance on x-ray
Soap bubble appearance on x-ray is associated with what tumor?
Giant cell tumor
What is the only bone tumor that arises in the epiphysis?
Giant cell tumor
Ewing sarcoma (what, where, who, x-ray, biopsy, translocation and prognosis)
Malignant proliferation of poorly-differentiated cells derived from neuroectoderm. Arises in the diaphysis of long bones; usually in male children (>15). Onion skin appearance on x-ray (layering of new bone by periosteum). Biopsy reveals small, round blue cells that resemble lymphocytes (can be confused with lymphoma or chronic osteomyelitis). t(11;22) translocation is characteristic. Often presents with metastasis, responsive to chemotherapy
Onion skin appearance on x-ray
Ewing sarcoma
Where do these tumors occur?
Osteoma
Osteoid osteoma
Osteochondroma
Osteosarcoma
Osteoma - surface of facial bones
Osteoid osteoma - cortex of long bones
Osteochondroma - lateral projection of the growth plate (metaphysis)
Osteosarcoma - metaphysis
Where do these tumors occur?
Giant cell tumor
Ewing sarcoma
Chondroma
Chondrosarcoma
Giant cell tumor - epiphysis
Ewing sarcoma - diaphysis
Chondroma - medulla of hands and feet
Chondrosarcoma - medulla of pelvis or central skeleton
