Osteopetrosis

Question 1

What is the defective cell in osteopetrosis?

Answer 1

Osteoclasts; unable to acidfy Howship’s lacunae which leads to dense bone and obliterated medullary cana

Question 2

What is the cellular mechanism responsible for osteopetrosis (Albers-Schönberg Disease)?

Answer 2

Carbonic anhydrase II; an enzyme that converts carbon dioxide and water into H+ and bicarbonate. The protons created are then transported across the ruffled border of osteoclasts, leading to acidification and demineralization of bone matrix.

Question 3

What are radiographic findings in osteopetrosis?

Answer 3

1) “erlenmeyer flask” proximal humerus and distal femur
2) “rugger jersey spine” with very dense bone
3) loss of medullary canal “bone within a bone” appearance
4) block femoral metaphysis

Question 4

What are some conditions a/w osteopetrosis?

Answer 4

1) cranial nerve palsies from overgrowth of skull foramina
optic > auditory > trigeminal > facial
2) osteomyelitis due to lack of marrow vascularity and impaired WBC function
3) long bone fractures (tension failure)
4) coxa vara from femoral neck fracture nonunion or repeated stress fractures