Flashcards in 18.1 Skeletal System Deck (72):
What, generally, is achondroplasia?
Impaired cartilage proliferation in the growth plate
What is the genetic cause of achondroplasia?
Activating mutation in FGFR3, causing inhibition of cartilage growth
What is the inheritance pattern of achondroplasia?
Most are sporadic, but if inherited, AD
What are the morphological characteristics of achondroplasia? What causes this phenotype?
Short extremities with a normal sized head and chest
-Long bones undergo endochondral bone formation
-Truncal bones undergo intramembranous bone formation
What happens to mental function, lifespan, and fertility with achondroplasia?
What is the intramembranous form of bone creation? What type of bones undergo this?
Bone is produced from a CT matrix
Bones of the skull, chest
What is the endochondral form of bone creation? What type of bones undergo this?
Cartilage produced, dies, and calcifies
What is the defect in osteogenesis imperfecta?
AD defect in collagen type I synthesis
What are the clinical features of osteogenesis imperfecta? (3)
Why are the sclera blue with osteogenesis imperfecta?
Exposure of the choroidal veins
What is osteopetrosis?
Inherited defect of bone resorption, resulting in abnormally thick, heavy bone that fractures easily
What is the pathogenesis of osteopetrosis?
Carbonic anhydrase II mutation results in lack of acidic environment required for resorption of bone
What is rxn that carbonic anhydrase catalyzes?
H2O + CO2 = H2CO3
What are the radiological characteristics of osteopetrosis?
Abnormally white and dense bones
What is Winter's formula? (from sitting in lecture) What is it for?
pCO2 = 1.5(HCO3)+8 +/- 2
What causes the anemia/ thrombocytopenia, and leukopenia with osteopetrosis?
Encroachment of bone on medulla of the bone
What causes the vision and hearing impairment of osteopetrosis?
CN impingement 2/2 ossification
What causes the hydrocephalus with osteopetrosis?
Ossification of the foramen magnum
What causes the acidosis with osteopetrosis?
Carbonic anhydrase deficiency results in a loss of bicarb in the blood, and an inability to excrete acid into the urine
What is the treatment for osteopetrosis?
Bone marrow transplant, which causes new and better osteocyte formation
What is the defect in rickets/osteomalacia?
Defective mineralization of osteoid 2/2 low levels of vit D
What are the four main causes of Vit D deficiency?
-Decreased sun exposure
-Liver failure and renal failure
When does rickets usually present?
Less than 1 year old
What are the clinical features of rickets? (4)
-Pigeon breast deformity
-Bowing of legs
What is depositied in abnormal places with rickets?
What is osteomalacia?
Low vit D in adults results in weak bone with an increased risk for fractures
What happen to serum Ca levels with osteomalacia?
What happen to serum phosphate levels with osteomalacia?
What happen to serum PTH levels with osteomalacia?
What happen to serum alk phos levels with osteomalacia?
What is the role of alk phos?
Used by osteoblasts to create an alkaline environment for bone to be laid down
What diseases is characterized by a loss of trabecular bone mass?
What are the three factors that determine the peak bone mass?
3. Vit D receptor inheritance
What is the age that bone mass peaks?
30 years old
The risk of osteoporosis is based on what two factors?
Peak bone mass and rate of bone loss thereafter
What are the two most common form of osteoporosis?
What are the clinical features of osteoporosis?
Bone pain and fractures in weight bearing areas
What happens to serum Ca with osteoporosis?
What happens to serum PTH with osteoporosis?
What happens to serum phosphate with osteoporosis?
What happens to serum alk phos with osteoporosis?
How is bone density measured?
True or false: there are no abnormal labs with osteoporosis
What defines osteoporosis vs osteopenia?
Osteopenia = -1 to -2.4 SDs
Osteoporosis = -2.5 and lower
What is the treatment for osteoporosis?
What is the MOA of bisphosphonates in treating osteoporosis?
Binds to phosphate in bone, and inhibits osteoclastic action (causes apoptosis of osteoclasts)
What is the general pathophysiology of Paget's disease of bone?
Imbalance between osteoclast and osteoblast action--first over osteoclast action, followed by osteoblast action that produce crappy bone
When does Paget's disease of bone usually present?
Late adulthood (60s)
True or false: Paget's disease of bone usually involves the entire skeleton
False--usually one or more, but not entire skeleton
What are the three general stages of Paget's disease of bone?
What is the end result of Paget's disease of bone?
Thick, sclerotic bone that fractures easily
What are the histological characteristics of Paget's disease of bone?
Tons of eosinophilic bone, with lines that have not been sealed
("Jigsaw puzzle" pattern)
Jigsaw puzzle bone = ?
Paget's disease of bone
What are the classic features of Paget's disease of bone?
-Increased hat size
-Lion-like facies 2/2 bone malformation
What lab is classically elevated in Paget's disease of bone?
What are the two major drugs that are used to treat Paget's disease of bone?
What causes the high output cardiac failure with Paget's disease of the bone?
Proliferation of AV shunts in bones increases CO
What cancer are patients with Paget's disease at increased risk for?
Osteosarcoma (malignant proliferation of osteoblasts)
Where does osteomyelitis usually come from?
Hematogenous spread to bone
Where in the bone is osteomyelitis usually seen? (kids, adults)
Metaphysis in kids
Epiphysis in adults
Is osteomyelitis usually bacterial, fungal, or viral?
What is the most common bacteria that causes osteomyelitis?
What is the most common bacteria that causes osteomyelitis in sickle cell patients?
What are the patients that get osteomyelitis 2/2 pseudomonas?
DM and drug abusers
What bone does TB classically infect?
What are the clinical features of osteomyelitis?
Bone pain with leukocytosis and fever
What are the radiological findings of osteomyelitis?
Lytic focus surrounded by sclerosis
How can you diagnose osteomyelitis?
What, generally, is avascular (aseptic) necrosis?
ischemic necrosis of the bone and bone marrow
What are the causes of avascular (aseptic) necrosis?
What are the major complications of avascular necrosis?