Skeletal dysplasia

Question 1

Most common form of short-limbed dwarfism

Answer 1

Achondroplasia

Question 2

Inheritance of achondroplasia?

Answer 2

Autosomal dominant, 80% new mutations

Question 3

Most consistent sonographic finding in achondroplasia?

Answer 3

Short long bones, esp femur, btw 21-27w (<3rd percentile) - but important finding is initially normal 1st & 2nd trimester measurements

Question 4

Other sonographic features of achondroplasia

Answer 4

Normal shape of femur
Macrocrania
Frontal bossing
Protuberant abdomen
Trident-shaped hand
Polyhydramnios

Question 5

What is diastropic dysplasia?

Answer 5

A recessively inherited form of short-limbed dwarfism, with the additional findings of thickening of the external ear and the characteristic “hitch-hiker” thumbs.

Question 6

What is achondrogenesis?

Answer 6

A lethal, recessively inherited condition, there is deficient ossification of the vertebral bodies. As compared with achondroplasia, a greater discrepancy between head size and trunk exists in achondrogenesis.

Question 7

What is Ellis-van Creveld syndrome?

Answer 7

Chondroectodermal dysplasia
Progressive distal shortening of the extremities and postaxial polydactyly are present
Congenital heart malformations are present in 50% of cases.

Question 8

What is hypochrondroplasia?

Answer 8

The major findings are short stature and an increased upper-to-lower body segment ratio. The facial features are within normal limits.

Question 9

What is the gene mutation in achondroplasia?

Answer 9

FGFR3

Question 10

What is the most common lethal skeletal dysplasia?

Answer 10

Thanatophoric dysplasia

Question 11

What are the classic features of thanatophoric dysplasia?

Answer 11

Cloverleaf skull in Type II
Micromelic limbs
Short ribs
Narrow thorax
Relative macrocephaly
Frontal bossing
Mid-face hypoplasia, 
Reduced height of the vertebral bodies
Central nervous system abnormalities

Question 12

Definition of micromelia

Answer 12

Shortening of the extremities involving the entire limb

Question 13

Definition of rhizomelia

Answer 13

Shortening of the extremities involving the proximal segment

Question 14

Definition of mesomelia

Answer 14

Shortening of the extremities involving the intermediate segment

Question 15

Definition of acromelia

Answer 15

Shortening of the extremities involving the distal segment

Question 16

Characteristics of osteogenesis imperfecta

Answer 16

Blue sclerae
hearing abnormalities
defective dentition
hyperlaxity of the joints
normal intelligence

Question 17

Types and severity of OI?

Answer 17

Type I is the common mild form, type II is the perinatal lethal form, type III is the severe form, and type IV is the moderately clinically severe form.
More recently, an additional three types (V, VI, and VII) have been described.
The clinical severity of OI is type II> type III> types IV = V = VI = VII > type I.

Question 18

What is campomelic dysplasia?

Answer 18

Symmetric bowing of the long bones of the lower extremities - acute femoral angulation, which typically occurs at the junction of the upper third and lower third of both femora, with resulting symmetrical shortening
Phenotypic sex reversal in some chromosomally male infants
Associated abnormalities including cleft palate, flat facies, micrognathia, hydrocephalus, and renal abnormalities.

Question 19

What is short-rib polydactyly syndrome?

Answer 19

A group of rare, generally lethal skeletal dysplasias

Short horizontal ribs and long tubular bone changes that result in severe micromelia.