Skeletal Dysplasias

Question 1

What are the 4 zones of the growth plate?

Answer 1

Reverse
Proliferative (achondroplasia)
Hypertrophic (SH frx)
Calcification (type 2>10 cartilage)

Question 2

Achondroplasia: inheritance and gene

Answer 2

AD - but 90% are sporadic mutation (not inherited)
FGFR3 activating mutation
Chr4
Glycine -> arginine @position 380

Question 3

Clinical features achondroplasia

Answer 3

Rhizomelic dwarfism - prox > distal growth arrest
Abnormal facies
Trident hands - cant approximate long and ring
Champagne glass pelvis - wider than deep
TL kyphosis
Lumbar stenosis - short pedicles
Posterior radial head dislocation

Question 4

What anatomic change can suddenly kill achondroplasia

Answer 4

Foramen magnum stenosis -> apnea or SIDS

Question 5

Surgical interventions for achondroplasia

Answer 5

Urgent decompression for cervical stenosis
Elective decompression lumbar stenosis
+/- genu varum osteotomies
+/- lengthening

Question 6

Pseudoachon: inheritance and gene

Answer 6

AS
COMP gene
Chr 19
Abnormal epiphysis + metaphyseal flaring

Question 7

Pseudoachon: clinical features

Answer 7

Rhizomelic dwarfism

NORMAL facies

Question 8

Pseudoachon: surgical interventions

Answer 8

+/- cervical stabilization

+/- genu varum osteotomies

Question 9

Disease w/ cauliflower ears + hitchhiker thumbs

Answer 9

Diastrophic dysplasia

• Cleft palate
• Joint contractures

Question 10

Diastrophic dysplasia: inheritance and gene

Answer 10

AS
DST DT gene
Chr 5
Sulfate transport protein - under sulfate proteoglycans

Question 11

Diastrophic dysplasia: surgical interventions

Answer 11

+/- ST releases or LE deformity
+/- spinal correction
Cauliflower ear compressive bandaging

Question 12

Cleidocranial dysostosis: inheritance and gene

Answer 12

AD - think, the orthobullets picture is dad daughter combo
RUNX mutation -> core binding factor alpha gene (CBFA)
Aka mutated osteoclacin TF
Affects INTRAmembranous ossification: skull, clavicles, pelvis

Question 13

Cleidocranial dysostosis: clinical features

Answer 13

Prolonged baby teeth
Clavicle aplasia
Coxa vara - only one you might treat with osteotomies if NSA < 100deg

Question 14

When you think of all the mucopolysaccharidoses, what is the most common inheritance and surgical intervention?

Answer 14

AR - except Hunter (X linked recessive)

C spine instability -> fusion

Question 15

Multiple epiphyseal dysplasia: inheritance and gene

Answer 15

AD
COMP and collagen gene mutations
Chr 19
Mutates type 9 collagen (a linker protein for t2 col) -> type 2 collagen dysfxn
Failure of 2ary ossification formation
Epiphysis forms wrong -> cartilage forms wrong

Question 16

Multiple epiphyseal dysplasia: clinical features

Answer 16

Proportional dwarfism 
Normal height early on -> dx mid-childhood 
NO spinal involvement 
Normal facies, intelligence 
Valgus legs (osteotomies)
Double layer patella 
If bilateral Perthes, r/o MED
Early onset OA (early total joints)

Question 17

Describes spondyloepiphyseal dysplasia as it differs from MED

Answer 17

• Mutation to t2 collagen directly (also AD)
• Affects proliferative zone
• Spine IS involved: cervical instability

Question 18

What is nail patella syndrome?

Answer 18

Mutation in Lim TF
Aplasia of patellas and condyles
Posterior dislocation of radial head (also seen achondroplasia)
1/3 adults develop renal failure and glaucoma