1.1 Skeletal System Flashcards
Achondroplasia
- clinical findings
- etiology
-dwarfism
- poor endochondral bone (long bones) formation
- intramembranous (head, chest) not affected
- mutation of FGFR3
- fibroblast growth factor receptor 3
- auto dominant
osteogenesis imperfecta
- what is it
- clinical findings (3 big ones)
- congenital defect in Type I collagen synthesis, weak bone
- auto dom.
- multiple fractures–mimic child abuse
- blue sclera–loss of type I collagen reveals underlying blue choroidal veins
- hearing loss–middle ear bones fracture
Osteopetrosis
- what is it, etiology
- Tx
“rock like”
- inherited defect of bone resorption
- results in thick bone that is paradoxically weak.
-Carbonic Anhydrase II mutation–normally required in osteoclasts to excrete H+, providing acidic environment for bone resporption.
- Bone marrow transplant
- osteoclasts come from monocytes
Osteopetrosis
-clinical findings (5 big ones)
- bone fractures
- bone impinges into bone marrow–anemia, thrombocytopenia, leukopenia
- bone impinges on cranial nerves–vision/hearing loss
- bone narrows foramen magnum–hydrocephalus
- Renal tubular acidosis–lack of carbonic anhydrase II leads to metabolic acidosis. (CAII required to excrete H+ and reabsorb HCO3-)
Why is bone marrow transplant the Tx for osteopetrosis?
Osteopetrosis is genetic loss of CAII inside osteoclasts, which come from monocytes.
-bone marrow will replace faulty monocytes, which develop into osteoclasts
Osteomalacia (Ricketts)
- etiology
- clinical findings
-low Vit D, leads to low Ca2+ and phosphate, which leads to defective mineralization osteoid
osteoid
- what osteoblasts produce.
- osteoid is then mineralized with calcium and phosphate to become bone.
Vit D:
- how is it acquired and activated?
- what does is act on?
-diet and UV light
- must be activated:
1. first in liver (to 25-OH-D)
2. then in kidney (to 1,25-OH-D) active form - increases Ca and phosphate reabsorption from:
1. GI
2. Bone
3. Kidney
Osteomalacia (Ricketts)
-clinical findings, child vs adult
-adult: weak bone
- child:
1. pigeon-breast deformity
2. frontal bossing (enlarged forehead)
3. Rachitic rosary (“beads”) in costochondral junction
4. bowing of legs
osteomalacia (Ricketts)
- lab findings:
- calcium
- phosphate
- PTH
- alkaline phosphatase
- calcium: low
- phosphate: low
- PTH: high
- alkaline phosphatase: high because basic environment necessary for osteoid mineralization by osteoclast (secreted by osteoclast)
Osteomalacia (Ricketts)
-causes (5)
- Diet
- Malabsorption
- Low sun exposure
- Liver disease
- Kidney disease
- both liver and kidney required to activate Vit D.
Osteoporosis
-what test used to measure
-DEXA scan to measure bone density
Osteoporosis
- lab values:
- calcium
- phosphate
- PTH
- alkaline phosphatase
all normal
Osteoporosis:
- tx
- contraindications
- Vit D, Calcium, exercise
- bisphosphonates–induce apoptosis of osteoclasts that eat them
- estrogen replacement–not recommended
- glucocorticoids–contraindicated
Paget Disease of Bone
- etiology, mech
- stages
‘paget’s puzzle pieces’
- imbalance btwn osteoclast and osteoblast function
- 3 stages:
1. osteoclast overactive
2. osteoblast tries to lay down bone in a rush
3. osteoclasts burn out, osteblasts still lay down bone
bisphosphonates
- induce apoptosis in osteoclasts when they eat them. reduce bone resorption
- tx in:
- Paget’s disease of bone
- Osteoporosis
Osteomyelitis
- etiology
- clinical findings
- difference child vs adult
- infection of bone and marrow
- inside bone–abscess (sequestrum) surrounded by sclerosis of bone (involucrum)
- child: metaphysis seeded
- adult: epiphysis seeded
involucrum
-sclerotic bone tissue that surrounds abscess in osteomyelitis
sequestrum
-abscess in bone from osteomyelitis
what can gas emboli do to bone?
cause ischemia, leading to avascular necrosis
osteomyelitis:
categories
- hematogenous
- direct implantation (penetrating injury)
- contiguous (direct infection from wound/ulcer)
- prosthetic infection
direct implantation osteomyelitis
-what pathogens?
- pseudomonas
- enjoys living in damp foot under socks and shoes
contiguous osteomyelitis
- common cause?
- what pathogens?
- diabetic foot ulcer
- think bugs that live in pressure ulcers:
- S aureus, G-‘s, strep, anaerobes, candida
hematogenous osteomyelitis
-what pathogens?
-S aureus, strep, G-, TB, salmonella
