2.1 Bone and Joint Pathology

Question 1

impaired cartilage proliferation in the growth plate, common cause of dwarfism

Answer 1

achondroplasia

Question 2

What is the activating mutation in achondroplasia?

Answer 2

FGFR3, autosomal dominant, inhibits growth

Question 3

What is the defect in osteogenesis imperfecta?

Answer 3

defect in collagen type I synthesis (usually autosomal dominant)

Question 4

Congenital defect of bone formation resulting in structurally weak bone

Answer 4

osteogenesis imperfecta

Question 5

clinical features of this disease include multiple fractures of bone, blue sclera (thinning of scleral collagen reveals underlying choroidal veins) , and hearing loss (bone of middle ear easily fractures)

Answer 5

osteogenesis imperfecta

Question 6

vitamin C deficiency

Answer 6

scurvy

Question 7

Can occur in infants fed only pasteurized milk for 1 year, , chronic alcoholics, sailors,

Answer 7

scurvy

Question 8

Pathogenesis of scurvy?

Answer 8

impaired type I collagen synthesis, vitamin C necessary for hydroxylation of procollagen

Question 9

Inherited defect of bone resorption resulting in abnormally thick, heavy bone that fractures easily

Answer 9

osteopetrosis

Question 10

osteopetrosis is due to poor ______ function

Answer 10

osteoclast

Question 11

mutation of _________ leads to loss of acidic microenvironment required for bone resorption in osteopetrosis

Answer 11

carbonic anhydrase II

Question 12

Why do you have anemia, thrombocytopenia, and leukopenia with extramedullary hematopoiesis in osteopetrosis?

Answer 12

due to bony replacement of marrow

Question 13

bone fractures, anemia, thrombocytopenia, vision and hearing impairment (impingement on cranial nerves), hydrocephalus (narrowing of foramen magnum), renal tubular acidosis (carbonic anhydrase II mutation)

Answer 13

osteopetrosis

Question 14

treatment for osteopetrosis?

Answer 14

bone marrow transplant, osteoclasts are derived from monocytes

Question 15

reduction in trabecular bone mass, results in porous bone with an increased risk for fracture

Answer 15

osteoporosis

Question 16

most common forms are senile and postmenopausal, peak bone mass at age 30

Answer 16

osteoporosis

Question 17

clinical features: bone pain and fractures in weight bearing areas (vertebrae, hip, radius), serum calcium, phosphate, PTH and alk phos normal (helps to exclude osteomalacia)

Answer 17

osteoporosis

Question 18

treatment: exercise, vit D, and calcium, bisphosphonates (apoptosis of osteoclasts)

Answer 18

osteoporosis

Question 19

Rickets/Osteomalacia has defective mineralization of ____

Answer 19

osteoid (osteoblasts normally produce osteoid, which is then mineralized with calcium and phosphate to form bone)

Question 20

Rickets/Osteomalacia is due to low levels of ________ which results in low serum _______ and ______

Answer 20

vitamin D, calcium and phosphate

Question 21

low vitamin D in children, resulting in abnormal bone mineralization, present with pigeon breast deformity, frontal bossing (osteoid deposition on skull), rachitic rosary (osteoid deposition at costchondral junction), bowing of legs

Answer 21

Rickets

Question 22

low vitamin D in adults, inadequate mineralization results in weak bone with an increased risk for fracture, lab findings: decreased serum calcium and phosphate, increased PTH and alk phos

Answer 22

osteomalacia