Achondroplasia

Question 1

True or False: Achondroplasia is the most common condition associated w severe disproportionate short stature

Answer 1

True!

Question 2

How is Achondroplasia inherited?

Answer 2

Autosomal dominent, although 75% are NEW dominant mutations

Question 3

True or false: advanced maternal age is associated with increased risk of achondroplasia

Answer 3

FALSE! Advanced paternal age is associated with achondroplasia and occurs almost exclusively in spermatogenesis

Question 4

What gene is affected in achrondroplasia?

Answer 4

Fibroblast growth factor receptor 3 (FGFR3) gene

Question 5

What can happen if both parents have achondroplasia and they decide to have a child?

Answer 5

Can have two bad scenarios:

1. Double heterozygosity (life-threatening)
2. Homozygosity (stillborn/die shortly after birth)

Question 6

What are 2 MSK features of achondroplasia

Answer 6

1. Bowing of lower legs

2. Proximal limb shortening

Question 7

What is a common ENT complication?

Answer 7

Otitis media causing hearing loss

Question 8

What are 2 developmental features of achondroplasia?

Answer 8

1. Delayed motor milestones

2. Normal intelligence

Question 9

What are 2 respiratory features of achondroplasia

Answer 9

1. Restrictive pulmonary disease if <3yo

2. OSA

Question 10

Name 4 facial features of achondroplasia

and 3 Body features

Answer 10

1. Flattened midface
2. Prominent forehead
3. Macrocephaly
4. Dental malocclusion
5. Normal length trunk
6. Trident shaped hands
7. Proximal shortening of long bones

Question 11

What are 4 uncommon but serious complications associated with achondroplasia?

Answer 11

1. Hydrocephalus
2. Craniocervical junction compression
3. Upper a/w obstruction
4. Thoracolumbar kyphosis

Question 12

Name 5 radiographic features of achondroplasia

Answer 12

1. Square shaped pelvis with a small sacrosciatic notch
2. Short pedicles of vertebrae
3. Proximal femoral lucency
4. Chevron shape of distal femur (inverted V shape)
5. Proximal shortening of long bones

Question 13

How do you diagnose achondroplasia?

Answer 13

Clinically, only do molecular testing if atypical.

Question 14

Why are CT/MRI commonly done in children with achondroplasia?

Answer 14

To asses the foramen magnum size.

note you should monitor head circumference closely in the first 2 years

Question 15

How often should hearing be checked in achondroplasia?

Answer 15

Annually.

Question 16

What are 3 special considerations for children with achondroplasia.

Answer 16

1. No unsupported sitting until trunk muscles fully developed, and avoid curved or “C sitting” in the first year of life as it can increase risk of kyphosis
2. Greater than average sweating is normal
3. Psychosocial impact of short stature (adapt environment)

Question 17

What is the natural history of achondroplasia?

Answer 17

1. Average adult height approx 4ft
2. Normal lifespan
3. Normal intelligence

Question 18

What is a longterm complication that can occur with achondroplasia?

Answer 18

1. Lumbosacral spinal stenosis w compression of spinal cord/nerve roots

Question 19

What are 2 special considerations for pregnant women with achondroplasia

Answer 19

1. Mom can have respiratory compromise

2. C/S required for delivery due to small pelvis size.