Bone tissue pathology Flashcards
Achondroplasia –> problem
failure of longitudinal bone growth (endochondral ossification) –> short limbs
Achondroplasia –> appearance
short extremities with normal sizes head and chest
large head RELATIVE to limbs
Achondroplasia –> membranous ossification
not affected (normal head and chest)
Achondroplasia –> pathophysiology
constitutive activation of FGFR3 –> inhibits chondrocyte proliferation –> impaired cartilage proliferation in growth plate –> impaired endochondral ossification
mutation in achondroplasia
FGFR3 (activation)
Achondroplasia –> sporadic vs inherited mutation
> 85% sporadic
Achondroplasia –> inherited type - mode of inheritance
AD (if homozygosity –> lethal)
homozygotic achondroplasia
lethal
Achondroplasia is the MCC of
dwarfism
Dwarfism is
a condition of short stature
MCC of Dwarfism
achondroplasia
achondroplasia - mental function
normal
achondroplasia - life span
normal
achondroplasia - fertility
normal
achondroplasia - sporadic mutation frequency is increased with
paternal age
osteopetrosis is also called
marble bone disease
osteopetrosis (marble bone disease) - pathophysiology
Carbonic anhydrase –> impair ability of osteoclast to generate acidic environment (necessary for bone resorption) –> thickened, dense bones
thickened, dense bones of osteopetrosis prone to
fractures
osteopetrosis - clinical manifestations (why)
- pancytopenia (bone fills marrow space)
- extramedullary hematopoiesis (bone fills marrow)
- cranial nerve inmpingement and palsies (narrowed foramina)
- hydrocephalus (narrowing of the foramen magnum)
- bone fractures
- Renal tubular acidosis (carb anhydr II mut)
foramen magnum?
the hole in the base of the skull through which the spinal cord passes.
osteopetrosis - nerve inpingemeted and palsies can cause
vision and hearing impairment
osteopetrosis - renal involvement
renal tubular acidosis (carb anhydr II mut) –> decreased tubular reabsorption of HCO3- –> metabolic acidosis
osteopetrosis - X-RAY appearance
bone - in - bone appearance
osteopetrosis - cranial nerve inmpingement and palsies due to
narrowed foramina
osteopetrosis - hydrocephalus due to
narrowing of the foramen magnum
treatment of osteopetrosis (why)
Bone marrow transplant is potentially curative as osteoclasts are derived from monocytes
types of osseous tissue
- cortical bone
2. trabecular bone
trabecular bone is also called
spongy bone
Primary osteoporosis?
trabecular (spongy) bone loses mass an interconnections despite normal bone mineralization and lab values
primary osteoporosis - Ca2+ leves
normal
primary osteoporosis - Pi leves
normal
primary osteoporosis - diagnosis by
- bone mineral density test (DEXA)
2. fragility fracture of hip or vertebra
DEXA - osteoporosis if
T-score less than -2.5
2ry osteoporosis can be caused by
A. DRUGS (1. long term exogenous steroid use 2. anticonvulsants 3. anticoagulants 4. thyroid replacement therapy 5. alcohol)
B. OTHER medical conditions (1. hyperparathyroidism 2. hyperthyroidism 3. MM 4. malabsorption syndromes)
primary osteoporosis can lead to
- vertebral compression fractures
- fractures of femoral neck
- distal radius fracture
distal radius fracture is also called
Colles fracture
vertebral compression fractures - presentation
- acute back pain
- loss of height
- kyphosis
Colles fracture is
distal radius fracture
primary osteoporosis types
type 1 (post-menopausal) type 2 (senile)
type 1 (post-menopausal) osteoporosis - mechanism
decreased estrogen levels –> increased bone resorption
osteoporosis - alkanine phosphate levels
normal
type 2 (senile) affects
men and women >70 years old
primary osteoporosis - prophylaxis
- regular weight bearing exercise
- Ca2+ and vitamin D intake throughout adulthood
primary osteoporosis - treatment
- biphosponates
- PTH analogs
- SERMs
- calcitonin
- denosumab
primary osteoporosis - treatment - mechanism of biphosponates
induce apoptosis of osteoclasts
denosumab - mechanism of action
monoclonal antibody against RANKL
Vitamin D deficiency can cause
adults –> osteomalacia (defective mineralization of osteoid)
children –> rickets (defective mineralization of cartilaginous growth plates)
Vitamin D deficiency –> condition of bones (mechanism)
Vitamin D deficiency –> defective mineralization/calcification of osteoid –> soft bones that bow out