Bone disorders

Question 1

Achondroplasia

Answer 1

FGFR3 gene mutation - GOF always on
inhibit chondrocyte proliferation

Becomes AD heredity - homozygous dominant die in utero, assume Aa for genetics

proximal long bones shorter than distal
bowing of tibias
frontal bossing

Question 2

Vit D deficiency

Answer 2

Kids - rickets
Adults - osteomalacia

decreased serum Ca2+ –> poor mineralization, soft bones

Question 3

Osteopetrosis

Answer 3

osteoclasts falling behind

XR: erlenmeyer flask at ends of bones

Defect in bone resorption
osteoclasts deficient in carbonic anhydrase II (can’t acidify)

pancytopenia
hearing loss

Question 4

Osteitis fibrosa cystica (AKA von Recklinghausen disease of bone)

Answer 4

Hyperparathyroidism or Type 1A pseudohypoparathyroidism (aka Albright hereditary osteodystrophy)

Cause high PTH –> excess osteoclastic activity

Brown tumors in bone - cystic spaces filled with fibrous stroma and blood

DEXA: low bone mineral density

Question 5

Paget Dz of bone

Answer 5

increased osteoclast activity followed by increased osteoblast activity

osteoclasts burn out

localized disorganized bone architecture - mosaic pattern

sx: bone pain, bone deformity, fx, increased hat size
or asx

may have hearing loss d/t narrowing auditory foramen

Increased risk of osteosarcoma

Question 6

Polyostotic fibrous dysplasia

Answer 6

Part of McCune Albright Syndrome (w/ precoious puberty, cafe-au-alit spots)

bone displaced by collagen and fibroblasts

irregular bony trabeculae