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Question 1

What is dysostosis

Answer 1

Developmental anomalies due to abnormal mesenchymal cell migration or differentiation into cartilage analogue

3 types: aplasia, supernumeray digits, syndactly/craniosyntosis

Question 2

Brachydactyly types D and E are due to mutations of what gene; what is seen with this disorder?

Answer 2

Mutations in homeobox HOXD13 gene

• Shortening of the terminal phalanges of thumb and big toe

Question 3

Cleidocranial dysplasia

mutation

Answer 3

AD: LOF RUNX2 transcription factor

Question 4

Achondroplasia, the most common skeletal dysplasia has which type of inheritance pattern and is due to what mutation?

Answer 4

AD: GOF in FGFR3

Question 5

what mutations can cause ABNL bone denisites

Answer 5

LPR5-R mutations on osteoblasts: osteoporosis or osteopetrosis

RANK-L mutations: decreased or absent osteoclasts => osteopetrosis

Question 6

inheritance in Osteogenis Imperfecta (brittle bone dz) type 1 and 2

Answer 6

• 1 = AD
• 2 = AR

Question 7

Other mutation for Osteopetrosis

Answer 7

CLCN7 gene on Chr8q22 => encodes proton pumps on surface of osteoclasts

Question 8

What do you see on XR in rickets and osteomalacia

Answer 8

1. Osteopenia (DEC bone mineral density)
2. Pseudofx (looser zones) = bands of low bone density that look like fractures