Bone Disease Part 4

Question 1

What are the 3 main congenital bone diseases

Answer 1

• Brittle bone disease (osteogenesis imperfecta)
• Achondroplasia
• Osteopetrosis

Question 2

what is another name for brittle bone disease

Answer 2

osteogenesis Imperfecta

Question 3

what is the cause of brittle bone disease

Answer 3

defective synthesis of collagen I and disruption of the structure of triple helix

Question 4

what does brittle bone disease result in

Answer 4

results in fragile skeleton and too little bone

Question 5

where are extra skeletal manifestations of brittle bone disease found

Answer 5

Extra skeletal manifestations of brittle bone disease found on: skin, joints, eyes: (blue sclera)

Question 6

6. How many types of brittle bone disease exist

Answer 6

4 types

Question 7

describe the clinical outcome of type I brittle bone disease

Answer 7

increased childhood fractures (pre-puberty) but normal stature

Question 8

describe the clinical outcome of type II brittle bone disease

Answer 8

fatality in utero or perinatal babies

Question 9

describe the clinical outcome of type III brittle bone disease

Answer 9

can be progressive and deforming and short stature

Question 10

describe the clinical outcome of type IV brittle bone disease

Answer 10

increased childhood fractures and short stature

Question 11

1. What causes achondroplasia

Answer 11

Caused by mutation on the fibroblast growth factor receptor 3 resulting in activation

Question 12

what are genetic features of achondroplasia

Answer 12

(autosomal dominant and heterozygous)

Question 13

What does FGFR3 activation result in

Answer 13

FGFR3 activation inhibits chondrocyte proliferation: affects growth plates

Question 14

3. What happens to the growth plates in achondroplasia

Answer 14

Growth plates are disorganised and hypoplastic

Question 15

4. What bones are affected by achondroplasia

Answer 15

All bones that develop by endochondral ossification are affected

Question 16

In what 4 ways does achondroplasia affect stature?

Answer 16

• Short stature with stunted extremities (esp. proximal)
• bowed legs
• frontal bossing
• pronounced lordosis/kyphosis

Question 17

1. How is osteopetrosis characterised

Answer 17

by high bone mass

Question 18

2. How do you get osteopetrosis

Answer 18

It is inherited

Question 19

3. Why does osteopetrosis happen and what does this lead to?

Answer 19

happens due to interference with osteoclast formation and differentiation directly affecting their action, leading to defective bone remodelling

Question 20

4. what are features of bones affected by osteopetrosis

Answer 20

Dense ‘stone bone’ but brittle and easily fractured

Question 21

5. What does deposited bone stay as?

Answer 21

Remain as woven bone

Question 22

6. Give 4 clinical effects of osteopetrosis

Answer 22

• fractures
• spinal nerve compression (excess bone)
• recurrent infection (reduced bone marrow cavity).
• Hepatosplenomegaly

Question 23

why does hepatosplenomegaly happen in osteoporosis

Answer 23

happens due to haematopoiesis outside the bone.

Question 24

How can osteopetrosis be treated

Answer 24

Bone marrow transplant to provide healthy osteoclast precursors