Bone Pathology - Witrak Flashcards
What is the leading cause of bone fractures in our country?
Osteoporosis
What is osteopenia
Diffusely demineralized bone, can see on x-rays
Could be caused by: Osteoporosis (usually the case) Osteomalacia Malignancy Rare hereditary disorder (aka osteogenesis imperfecta)
What is the most common type of tumor you see in the skeleton?
metastatic tumors from other sites
What is a pathological fracture?
fracture through diseased bone (most often through tumorous bone)
Which bone cells secrete alkaline phosphatase?
Osteoblasts
What is sacrificed in the body in order to maintain ionized calcium at the right levels
Itegrity of the skeleton
Source of Vitamin D?
Sunshine in skin
what you ingest
What is required in order to have healthy bones?
In summary, for healthy bone:
Ca, P (from diet)
Vit D (from diet, skin synthesis)
gut (absorbing Ca, P, Vit D)
healthy kidney (makes Vit D (OH)2, resorbs/excretes Ca, P)
parathyroids (master gland for Ca, bone metabolism)
What is a salter fracture?
Epiphyseal plate injury that could lead to growth disturbance
What is fat embolism syndrome?
Usually occurs in people who have fractures. Fat travels to lungs and brain leading to shortness of breath, loss of consciousness, death…
Ostepenia below the age of 50… what might be some of the differentials diagnoses you might predict???
Due to excess corticosteroids (endogenous or exogenous) Hyperparathyroidism Hyperthyroidism Poor nutrition/malabsorption Immobilization Hypogonadism Multiple other disease associations
SEcondary problem due to kyphosis?
Poor ventilation due to hunch can lead to increased susceptibility of pneumonia
Best prevention to osteoporosois
max peak bone mass (teen/young adults) nutrition and stuff
Encourage weight-bearing exercise and Ca supplemnetation
What causes hypercalcemia?
primary hyperplasia or NEOPLASTIC enlargement of parathyroid glands
How can kidney disease affect the skeleton?
Secondary hyperparathyroidism (renal disease) may also produce gross skeletal change.
Classic indication of hyperparathyroidism?
Increase Ca and decreased Phosphorous
Is increased calcium important to look into?
Yes, you need to find out the cause
90% of all cases due to malignancy and hyperparathyroidism
Causes of osteomalacia:
Environmental: classic childhood rickets
Poor diet + sun exposure in northern latitudes
Intestinal malabsorption—commonest cause of Vit D deficiency in USA
Liver or renal disease (impaired hydroxylation of Vit D)
Rare congenital/inborn errors of metabolism
- Deficient Vit D hydroxylation
- Renal tubular phosphate leak
- End organ resistance to Vit D (OH)2
Difference in diagnosing osteoporosis and osteomalacia?
Osteomalacia has these signs:
Increased serum alkaline phosphatase (>90%)
Low serum Ca or P (50%)
Decreased urinary Ca excretion (33%)
Increased PTH (40%)
Decreased 1, 25 dihydroxyvitamin D3 (50%)
Where does Vit D come from and where is it hydroxylated?
Vit D comes from diet and skin synthesis
It is first hydroxylated in the liver and then secondly in the kidney
In the kidney, it is PTH that stimulates the hydroxylation
What stimulates secretion of PTH (parathyroid hormone)
Hypocalcemia
How do PTH and Vit D affect the Ca levels in the intestine, kidney, bone and blood?
Kidney
- PTH stimulates production of Vit D
- PTH increases Resorbtion of Ca
- PTH cause excretion of P
Bone
-Vit D and PTH stimulate transferring Ca from bone into the blood
Intestine
-PTH and Vit D stimulate increase in absorbtion of Ca and P from the intestine into the blood
Why is osteoporosis so common in older women?
- Ability of kidneys to hydroxylate Vit D(OH)1 to Vit D(OH)2 becomes impaired with age
- Diminished PTH secretion by parathyroid glands in response to hypocalcemia
- Increased osteoclastic activity
- Decreased ability of osteoblasts to make matrix
MOst common bacteria in suppurtative osteomyelitis?
Staph Aureus
What fungi cause fungal osteomyelitis?
Blastomycosis and coccidioidomycosis:
Commonest causes of fungal osteomyelitis in non-immunosuppressed patients
Almost always 2° to hematogenous spread from lungs; original pulmonary infection may have gone undiagnosed or be asymptomatic
Very painful location of osteomyelitis?
Vertebral osteomyelitis
Sickle cell patients tend to get what kind of infection in their bones? (osteomyelitis)
Salmonella
What it Paget’s Disease of bone?
Deforming bone disease of middle-aged to elderly adults
Current theory:
Due to a latent viral infection of osteoclasts in a genetically susceptible person
Affects up to 10-15% of elderly population (esp. Anglo-Saxon heritage)
Rare in Asians, Africa, India, Scandinavia
What are the three phases of Paget’s disease?
Lytic— increased osteoclasts with bone resorption/increased vascularity
Mixed—Increased osteoclasts with increased osteoblasts, increased vascularity
Sclerotic—most characteristic radiologically (osteoblastic phase)
What would you see in radiological images of Paget’s Disease?
Most patients asymptomatic
Widening / bowing of long bones
Distorted / widened pelvic bones
General weakening of affected bone causing increased fractures
Biochemically, as a physician you would suspect Paget’s if:
Older patient
Isolated increased alkaline phosphatase level
Normal serum calcium
No hepatobiliary disease
What is osteogenesis imperfecta?
Congenital disorders of type 1 collagen
Either qualitatively abnormal or quantitatively too little
Result:
-insufficient / inadequate collagen for normal osteoid production
- Osteopenia/osteoporosis
-tendency toward fractures
What is osteopetrosis?
Thicken bone, a lot more osteoblast rather than osteoclast activity
Loss of balance
Thick and chalk-like, so big but still easy to break
What can x-rays help to predict about tumours involving the bones?
Likelihood of primary vs metastatic lesion
Ability to subtype primary bone tumors by location and x-ray character
Usually accurate in separating benign from malignant lesions
By x-ray, tumors can be classified as either:
- osteolytic (demineralizing effect)
- osteoblastic (increased bone density relative to normal bone)
- mixed osteolytic/osteoblastic features
Example of purely osteolytic bone malignancy?
Myeloma
- Multifocal osteolytic lesions with bone pain
- Often associated hypercalcemia
- Fractures common
Example os purely osteoblastic bone malignancy?
metastatic prostate cancer
Why can leukemia sometimes be misdiagnosed as childhood rheumatoid arthritis?
acute leukemia alsways involves the bone marrow
Can produce diffuse bone or joint pain when the lymphocytes enter the periosteum
pain that almost seems like rheumatoid arthritis
What are bone fibromas?
CommonEST bone legion (not a neoplasm)
Can be found in 1/3 of growing children
Only a small fraction present clinically & need Rx
Pain
Pathologic fractures sometimes occur
Often spontaneously regress
CommonEST primary malignant tumor in:
Children
AND
Adults
Children: Osteosarcoma
AND
Adults: Chondorsarcoma
Abnormal thickening of the cortex of bones, usually long bones
osteoid osteoma
What kinds of bones do benign vs malignant cartilage tumors tend to involve?
Chondromas - small bones
Chondrosarcomas - large bones
epiphysis is targeted by this type of tumor
giant cell tumor
The most aggressive/lethal of all primary bone tumors?
Ewing’s sarcoma!
One thing I didn’t get: How does kidney disease even affect the skeleton?
Impaired kidneys lose the ability to remove phosphorus from the blood which causes serum phosphate levels to increase. Phosphorus is involved in the regulation of calcium, high blood levels of phosphorus cause calcium to drop. If calcium levels drop, the parathyroid glands in the neck secrete parathyroid hormone which pulls calcium from the bones to compensate. This gradually and silently weakens the bones.
Called renal osteodystrophy.
