Bones 1 Flashcards
What cells have RANK ligand?
Osteoblasts and marrow stoma cells
Where is the RANK receptor located?
Osteoclasts precursor
Allows OC generation and survival
Describe the M-CSF pathway
M-CSF secreted by OB
Receptor located on OC, allows OC generation and survival
What is the function of the WNT/B-catenin pathway?
WNT from marrow stomal cells binds LRP5 and 6 receptor on OB
Secretes OPG that blocks RANK
What substances make up bone?
Calcium hydroxyapatite
Organic matrix, mostly Type 1 Collagen
What are the two main types of bone?
Woven bone- random collagen deposition
Lamellar bone - ordered collagen deposition
What is osteopontin?
Unique to bone, levels parallel to osteoblast activity
What is alkaline phosphatase?
From osteoblasts
But also located in liver and placenta
What are the characteristics of woven bone?
Rapid bone growth - e.g. healing fracture
Resists forces in all directions
Always pathologic
What are the characteristics of lamellar bone?
Ordered collagen deposition
Replaces woven bone
Stronger than woven bone
What is intramembranous ossification?
Process of bone formation, direct from mesenchyme
Appositional growth
What is dysostosis?
Local problems in migration of mesenchyme and their condensation
What is dysplasia?
Global defect in regulation of skeletal organogenesis
What are the symptoms of Cleidocranial dysplasia?
Short stature
Abnormal clavicles
Supernumery teeth
Wormian bone
What is the cause of cleidocranial dysplasia?
RUNX2 transcription factor defect
What is the cause of achondroplasia?
FGFR3 point mutation, GoF mutation that inhibits cartilage growth
90% results from point mutation
If achondroplasia is hereditary, what is its inheritance pattern?
Autosomal dominant
Most common from paternal allele
What are the symptoms of achondroplasia?
Short stature
Short proximal limbs
Enlarged head with bulging forehead
Normal longeivity, intelligence, and reproduction
What is the cause of thanatophoric dwarfism?
FGFR3 mutation, GoF
Most common lethal dwarfism
“Cloverleaf” skull
What is osteopetrosis?
Diffuse systemic bone sclerosis
“Marble bone disease”
What are the possible causes of osteopetrosis?
Reduced osteoclast bone resorption, cannot acidify pit
Defect in RANKL - not enough OC activity
LRP5 GoF
What are the signs of osteopetrosis?
Bone deposition replaces medullary cavity
Bulbous long bones - erlenmyer flask deformity
Narrow neural foramina
Brittle bones
What is osteogenesis imperfecta?
Group 1 type 1 collagen diseases
Brittle bone disease
*can be confused with child abuse
What is the most common type of osteogenesis imperfecta?
Autsomal dominant
What are the signs of osteogenesis imperfecta?
Blue sclera
Dentinogenesis imperfeta
Hearing loss - abnormal ear bone
Joint laxity
Normal lifespan
What is osteoporosis?
Increased bone porosity and decreased mass
Can be from disuse or metabolic
Why is X-ray not sensistive for osteoporosis?
Can only detect only after 30-40% of bone loss
What is the difference between osteopenia and osteoporosis?
Osteopenia - decrease in bone mass
Osteoporosis- osteopenia to the point of risk of fracture
What is senile osteoporosis?
Mostly hereditary determined by Vit D receptor
Slow decrease in bone mass over time
Cortex thinned on all surfaces
Low turnover
What is the cause of postmenopausal osteoporosis?
Decreased estrogen leads to increased inflammatory cytokines
High turnover form
What is osteitis fibrosa cystica?
Severe form of hyperparathyroidism
Increased activity OC>OB
What is the most common cause of primary hyperparathyroidism?
Adenoma
How is the skeleton affected in hyperparathyroidism?
Subperiosteal resorption thins cortices
Loss of lamina dura around teeth
Affects entire skeleton
What are the characteristic x-ray findings of hyperparathyroidism?
Bone loss radial aspect of middle phalanges of index and middle finger
Osteopenia
What are brown tumors?
Bone replaced by fibrovascular tissue
Granulation tissue and hemosiderin
Characteristic of hyperparathyroidism
What are the symptoms of renal osteodystrophy?
Increased or decreased OC/OB activity
Hyperparathyroidism (secondary)
Decreased Vit D converstion
Metabolic acidosis: incrased calcium
What demographic does Paget disease affect?
Mid adulthood caucasians from US, Europe
What are the stages of Paget disese?
OSteolytic - loss of bone mass
Mixed - osteolytic and osteoblastic
Osteosclerotic - coarse thick irregular trabeculae
What characteristic xray finding is associated with early-stage paget’s disaese?
Blade of grass lesion
How does Paget disease present?
Pain from microfactures
Increased alkaline phosphatase
Normal Ca/PO4
Warm skin over affected bone
Tumors
How is Paget disease treated?
Calcitonin and biphosphonates
What is osteonecrosis?
Infarction of bone and marrow
Mechanisms that create ischemia
What is the most common cause of osteonecrosis?
Coritcosteroids
What is osteomyelitis?
Inflammation of the bone almost always from infection
What is the classic x-ray for osteomyeltitis?
Lytic bone lesion with surrounding sclerosis
What is the most common causitive bacteria if an osteomyeltitis culture is positive?
S. aureus
What is the common location of pyogenic osteomyelitis in a neonate, child, and adult?
Neonate - metaphysis and/or epiphysis
Children - metaphysis
Adualt - epiphysis and subchondral bone
What is a sequestrum?
Dead piece of bone
How many cases of osteomyeltitis become chronic osteomyelitis and why?
5-25%
Hard to reach area with antibiotics
What is the most common skin cancer associated with osteomyelitis?
Squamous cell carcinoma
What is the most common form of TB osteomyelitis?
Potts disease
What is Potts disease?
L/T spine
Break through dics to other vertebrae
Involve two vertebrae
What are the characteristic findings of syphilis of the bone?
Saddle nose - collapsed nose
Saber shin - tibia
