1. Achondroplasia :
Bone growth disorder that causes disproportionate dwarfism.
Dwarfism is defined as a condition of short stature as an adult.
Most common type of disproportionate Dwarfism.
Approximately 1 in 25,000 live births
Equally common in males and females.

2. Causes : Caused by mutations in the FGFR3 gene.
The FGFR3 gene instructs your body to make a protein necessary for bone growth and maintenance.
Mutations in the FGFR3 gene cause the protein to be overactive. This interferes with normal skeletal development.

3. Is achondroplasia inherited?
In more than 80 percent of cases, achondroplasia isn’t inherited.
Spontaneous mutations in the FGFR3 gene
National Human Genome Research Institute (NHGRI)
About 20 percent of cases are inherited.
One parent needs to pass down a defective FGFR3 gene for a child to have achondroplasia.
If one parent has the condition, the child has a 50 percent chance of getting it.

4. Both parents have the condition :
* 25 percent chance of normal stature
* 50 percent chance of having one defective gene that
causes achondroplasia
* 25 percent chance of inheriting two defective genes,
which called homozygous achondroplasia
( stillborn or die within a few months of being born)

5. Normal intelligence level
Symptoms :
Normal intelligence level
Short stature that’s significantly below average for age and sex
Short arms and legs, especially the upper arms and thighs, in comparison to body height
Short fingers in the ring and middle fingers

6. Disproportionately large head compared to the body
Abnormally large, prominent forehead
Underdeveloped area of the face between the forehead and
upper jaw

7. Health problems an infant may have include:
Decreased muscle tone, which can cause delays in walking and other motor skills
Apnea, slowed breathing or breathing that stops
Hydrocephalus, or “water on the brain”
Narrowing of the spinal canal can compress the spinal cord

8. Children and adults with achondroplasia may:
* Have difficulty bending their elbows
* Be obese
* Recurrent ear infections due to narrow passages in the ears
* Bowed legs
* Abnormal curvature of the spine called kyphosis or lordosis
* New or more severe spinal stenosis

9. How tall will child grow?
The average height for adult 4 feet, 4 inches for males and
4 feet, 1 inch for females
Children's Hospital of Philadelphia (CHOP).
Rare to reach a height of 5 feet.

10. Diagnosed : X-rays to measure the length of infant’s bones
Blood tests ( defective FGFR3 gene )
Ultrasound
( hydrocephalus, or an abnormally large head )
Genetic tests
( defective FGFR3 gene in a sample of amniotic fluid )

11. Treatment : There’s no cure or specific treatment
Antibiotics are given for ear infections
Surgery in severe cases of spinal stenosis
Growth hormones to increase the growth rate of a child’s bones

12. Long-term outlook : Normal life span
Increased risk of death during the first year of life
Increased risk of heart disease later in life.
Avoiding impact sports that could damage the spine

13. Further References :
Expand SectionCarson BS, Groves M, Yassari R. Neurologic problems of the spine in achondroplasia. In: Quiñones-Hinojosa A, ed. Schmidek and Sweet's Operative Neurosurgical Techniques. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 184.
Horton WA, Hecht JT. Disorders involving transmembrane receptors. In: Kliegman RM, Stanton BF, St. Geme JW III, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 696.

14. Q & A
Dr. 熊永萬
Dr. Bear