Bone Developmental Disorders

Question 1

Osteogenesis imperfecta

Answer 1

Congenital bone developmental disorder

• AD defect type I collagen
• blue sclera, hearing loss
• type II fatal in utero

Question 2

Achndroplasia

Answer 2

Congenital bone developmental disorder

• decreased chondrocytes at growth plate
• AD increased FGF-receptor 3 –> decreased chondrocyte proliferation
• MCC inherited dwarfism
• risk for brain injury if deformed foramen magnum

Question 3

Osteopetrosis

Answer 3

Congenital bone developmental disorder

• defective bone resorption
• either low # of osteoclasts (from low RANKL) or defective osteoclasts
• brittle bones, cranial nerve compression, pancytopenia, hepatosplenomegaly

Question 4

Osteoporosis

Answer 4

Acquired bone developmental disorder

• low bone mass
• post menopausal women
• low physical activity in youth
• age –> dec. osteoblast activity

Question 5

Paget Disease

Answer 5

Acquired bone developmental disorder

• Early phase (inc. resorption of bone), Mixed phase, Late phase (inc. formation of lamellar bone)
• Jigsaw puzzle appearance
• pain/deafness
• Increased risk for sarcoma

Question 6

Rickets/Osteomalacia

Answer 6

Acquired bone developmental disorder

• Failure of mineralization (defect in inorganic part)
• rickets in kids, osteomalacia in adults
• Rickets - Vit. D. deficiency
• poorly mineralized bone (much of bone not calcified)
• Von Kossa stain shows lack of calcification

Question 7

Renal Osteodystrophy

Answer 7

Acquired bone developmental disorder

• Decreased renal function leads to secondary hyper PTH
  1. causes dec. 1-alpha-hydroxylase
  2. causes phosphate retention
• inc. PTH –> inc. RANK-L –> inc. osteoclasts –> Osteoporosis
• brown tumors

Question 8

Hyperparathyroidism

Answer 8

Acquired bone developmental disorder

• primary - adenoma or parathyroid gland
• secondary - hypocalcemia/ESRD
• Osteitis Fibrosa Cystica = dec. bone mass –> ingrowth of reparative fibrous tissues –> brown tumor