metabolic bone dz Flashcards
RANK
receptor on osteoclasts which facilitates bone resorption when RANK-L binds to it.
OPG
osteoprotegerin- a decoy RANK-L receptor which decreases bone resorption
Risk factors for fragility fractures of osteoporosis
Previous Fractures, Age (increases after 55), Falls, Low Bone Mass
How do vertebral fractures affect fracture risk
Increases risk by 5% of having another fracture
compare osteoporosis vs osteopenia
Osteopenia: Bone mineral density T score of -1 to -2.5 Osteoporosis: bone mideral density T score of < -2.5. Normal: BMD T score of >-1.0
normal bone remodeling
Resorption= formation, OC= OB, old bone = new bone. Bone mass remains stable
Non-modifiable risk factors for low bone mass
Age, Race, Gender, Family History, Early Menopause
Modifiable risk factors for low bone mass
Low Calcium Intake, Low Vitamin D Intake, Estrogen Deficiency, Sedentary Lifestyle, Cigarette Smoking, Excess Alcohol (> 2/day), Excess Caffeine (> 2/day), Medications
How is diagnosis of osteoporosis/osteopenia made
measure bone density at and base T score on lowest density site
Who is treated for osteoporosis
Anyone with a fragility fracture, vertebral fracture, hip fracture or T score 3% risk of hip fracture of >20% major OP fracture
Osteoporosis prevention and treatment
- Ca- 1000-1500mg/day. Supplement if dairy intake insufficient. 2. Vitamin D. 3. exercise- aerobic and resistance. 4. falls- assess and prevent
osteoporosis treatment
- anti-resorptive agents: bisphosphanates, denosumab, raloxifene, calcitonin, estrogens. 2. anabolic agents: teriparatide, romosozumab
Define osteomalacia
impaired bone mineralization due to inadequate Ca and Phosphate resulting in soft, weak bones. Called rickets in kids
Causes of osteomalacia and rickets
- Vitamin D deficiencies- poor intake/sunlight, renal dz, hypoparathyroidism, congenital. 2. phosphate disorders- poor intak, renal phosphate wasting, congenital (Vitamin D resistant rickets- impaired Vit D formation or renal phosphate wasting)
clinical features of osteomalacia and rickets
osteomalacia: pain, deformities, fractures. Rickets: pain, deformities, muscle weakness, short stature
Osteomalacia/rickets labs
Decreased Ca, decreased phosphate, increased serum alkaline phosphatase, increased serum PTH, decreased urine Ca
osteomalacia radiology
fractures, pseudofractures- milkmans fractures, loosers lines
rickets radiology
Bowing of long bones, flaring ends of long bones, delayed epiphyseal calcification
osteomalacia/rickets treatment
- Nutritional Vitamin D Deficiency- Vitamin D and Calcium. 2. Congenital 1 Alpha Hydroxylase Deficiency- Calcitriol and Calcium. 3. Congenital Vitamin D Receptor Deficiency- High Dose Vitamin D or Calcitriol and Calcium. 4. Congenital Hypophosphatemic Rickets- Calcitriol and Phosphate
Define pagets
An Idiopathic Bone Condition Characterized by Excessive/Unregulated Bone Resorption and Formation
Etiology of pagets disease
genetic component (enhances osteoclast formation/reactivity) plus chronic paramyxovirus infection (induces changes in osteoclast precursors)
Gene linked to Pagets disease
Sequestosome I/ p26- a ubiquitin binding protein that induces NF-kB activation and osteoclast differentiation/activity/survival.
Clues to the viral cause of pagets disease
it is associated with dog owners, specific locations (rare in africa/asia), osteoclasts show paramyxovirus-like inclusions in nuclei + cytoplasm.
Pagets disease skeletal features
pain, deformity, fractures, osteoarthritis, hypervascularity, acetabular protrusion, osteogenic sarcoma. Commonly involves pelvis, skull, vertebrae, femur and tibia
Pagets disease neurological clinical features
deafness (8th nerve, ossicles), cranial nerve compression (bony), spinal cord compression (vascular)
Pagets disease cardiovascular features
Atherosclerosis, Aortic Stenosis, Congestive Heart Failure
(High Output)Atherosclerosis, Aortic Stenosis, Congestive Heart Failure
(High Output)
pagets dz over time
high osteoclast activity > osteoclast and osteoblast activity equal > osteoblast activity higher
Pagets dz labs over time
elevated NTX/CTX (bone resorption marker) > elevated NTX/ CTX and elevated alkaline phosphatase (bone formation marker) > decreased NTX/ CTX and elevated or decreased alk phosph
Pagets disease diagnosis
- elevated remodeling markers (NTX/ CTX, alk phos). 2. X ray features (very specific). 3. bone scan (very sensitive). 4. bone biopsy (occassionally needed)
Pagets radiology
- Osteolytic Lesions- “Blade of Grass” Sign in Long Bones, Resorption Front in Flat Bones (~1 cm/yr). 2. Osteosclerotic Lesions near Lytic Areas. 3. Thickened, Disorganized Trabeculae. 4. Thickened, Expanded Cortex. 5. Expansion of Bone Size
Pagets bone scan
Focal areas of intense uptake
Pagets histology
Increased Osteoclast Numbers, Increased Osteoclast Nuclei (20-100 per cell),Increased Osteoblasts in Periphery, Disorganized Mosaic Woven Bone
When to treat Pagets disease
Pagetic Pain, Deformity or Fracture, Weight Bearing Bone Involvement, Extensive Skull Involvement, Neurological Complication, Impending Surgery on Pagetic Bone, Immobilization Hypercalcemia, Alkaline Phosphatase > 2 x Normal
Pagets disease treatment
- anti-resorptive agents- bisphosphonates, calcitonin. 2. analgesics/NSAIDs. 3. corrective surgery
