E2L16-17, Non Neoplastic Bone Diseases Pathoma

Question 1

What causes achondroplasia?

Answer 1

Mutation activating FGFR3 receptor that causes decreased cartilage growth

Question 2

What parental factors affect achondroplasia?

Answer 2

Assoc. c increased paternal age

Question 3

What disease causes short limbs but normal head and trunk? Explain why.

Answer 3

Achondroplasia
Affects cartilage growth involved with endochondral ossification which affects limbs but not flat bones which use intramembranous ossification

Question 4

Inheritance pattern for achondroplasia

Answer 4

AD

Question 5

What disease can present with blue sclera and why?

Answer 5

Osteogenesis Imperfecta

Defect in Type I collagen synthesis in the sclera exposes the choroidal veins giving a blue appearance

Question 6

What causes Osteogenesis Imperfecta?

Answer 6

AD caused defect in the synthesis of Type I collagen leading to weak bone formation and fractures

Question 7

Besides fractures, what other Sx might a patient with Osteogenesis Imperfecta have?

Answer 7

Hearing loss because of the fragile bones in the ear

Question 8

What kind of an environment is needed to resorb bone?

Answer 8

Acidic environment is needed for proper functioning of osteoclasts so they can resorb bone

Question 9

What disease is caused by a defect in carbonic anhydrase II and why?

Answer 9

Osteopetrosis
Carbonic anhydrase catalyzes the conversion of water and CO2 into carbonic acid. This then dissociates into H+ and HCO3-. Osteoclasts use this reaction to create an acidic environment needed to resorb bone.

Question 10

Which non neoplastic bone disease is a myelophthisic process and what are the effects?

Answer 10

Osteopetrosis
Myelophthisic processes are those which crowd out the medullary space inside bone preventing hematopoiesis and therefore causing anemia, leukocytopenia, thrombocytopenia, extra-medullary hematopoiesis

Question 11

What is the cause of Osteopetrosis?

Answer 11

Many causes, most commonly a defect in carbonic anhydrase II enzyme which prevents the formation of acid by osteoclasts and prevents resorption of bone

Question 12

What are some of the additional Sx of osteopetrosis?

Answer 12

CN impingement, vision and hearing loss, renal tubular acidosis

Question 13

Explain the renal tubular acidosis seen with osteopetrosis

Answer 13

Osteopetrosis is commonly caused by a carbonic anhydrase deficiency. CA produces acid in the kidney so that it can be secreted. Without CA acid remains in the blood causing acidosis

Question 14

Treatment of osteopetrosis

Answer 14

Bone marrow transplant

Restores ability to produce normal functioning osteoclasts

Question 15

What disease manifests with rosary beads parasternally, pigeon-breast deformity, frontal bossing, and bowing legs?

Answer 15

Rickets

These Sx appear in kids who have deficiency of vit. D

Question 16

What is the pathogenesis of Rickets and Osteomalacia?

Answer 16

Deficiency of vit. D prevents the mineralization of osteoid that has been deposited by osteoblasts

Question 17

What labs might be seen in osteomalacia?

Answer 17

Low: Ca, Ph
High: PTH, AP

Question 18

How is alkaline phosphatase related to osteomalacia?

Answer 18

Osteomalacia is decrease in bone density caused by deficient levels of vit. D leading to low levels of minerals needed to mineralize bone.
Despite the lack of minerals, osteoblasts are still busy making osteoid and an alkaline environment is needed to deposit bone. AP creates the alkaline environment and is elevated because of increased osteoblast activity.

Question 19

What factors determine a woman’s peak bone mass?

Answer 19

Diet, Exercise, Vit. D receptor inherited

Question 20

What factors decrease the loss of bone in osteoporosis?

Answer 20

Diet, Exercise, Estrogen

Question 21

What are major differences between osteomalacia and osteoporosis?

Answer 21

Labs are abnormal in osteomalacia but normal in osteoporosis including Ca, Ph, PTH, AP

Question 22

Osteoporosis Treatment

Answer 22

Exercise, Diet, Vit. D, Calcium, Estrogen therapy

Question 23

What disease causes “Puzzle Piece” bone?

Answer 23

Paget’s disease

Question 24

What disease causes cement lines and a mosaic pattern of lamellar bone?

Answer 24

Paget’s disease

Question 25

What are the stages of Paget’s disease?

Answer 25

1) osteoclasts go crazy (unknown cause, possibly viral)
2) blast and clast activity
3) clasts seem to burn out and blast activity predominates
4) rapid bone formation causes thick and brittle bone

Question 26

Describe some of the major features of Paget’s disease of bone

Answer 26

Imbalance between blasts/clasts
Localized process (not systemic)
Late adulthood
Thick brittle bone, easy fractures
Cement lines and mosaic pattern
Bone pain, increased hat size, hearing loss, lion face, isolated increased AP

Question 27

What disease has an isolated elevated alkaline phosphatase?

Answer 27

Paget’s disease of bone

Question 28

Potential complications of Paget’s disease of bone

Answer 28

High-output cardiac failure from formation of A-V shunts
Osteosarcoma–think of the blasts getting out of control as they frantically try to rebuild bone after the osteoclast attack.

Question 29

How is osteomyelitis different between kids and adults?

Answer 29

Kids: metaphysis, hematogenous spread
Adults: epiphysis, often open wound somewhere

Question 30

Causes of osteomyelitis

Answer 30

S. aureus–most common
N. gonorrhea–sexually active
Salmonella–sickle-cell
Pseudomonas–diabetes or IVD
Pasteurella–dog/cat bite/scratch
TB–seen in vertebrae called Pott's disease

Question 31

Common bone finding in osteomyelitis

Answer 31

Lytic bone lesions surrounded by sclerosis

Question 32

Causes of avascular necrosis

Answer 32

trauma, fracturem steroids, sickle cell, caisson disease

Question 33

Complications of avascular necrosis

Answer 33

osteoarthritis and fracture