Achondroplasia (Dwarfism)

By. Shaira Hai

What is Achondroplasia?

Achondroplasia is a bone growth disorder that causes disproportionate dwarfism. Dwarfism is defined as a condition of short stature as an adult. People with achondroplasia are short in stature with a normal sized torso and short limbs.

History

Egypt

No Egyptian medical text mentions the body appearance as short. Upper Egypt, An expedition was led from Upper Egypt to the southern country of Yam, in the Sudan, and had brought back a small man from the land of the Akhtiu. The king of Egypt was astonished by this rarity when he saw the strange man. It is predicted these “small people”were African pygmies. In present times, most pygmy tribes migrate within the tropical forests and swamps of Central Africa, but they may have lived once farther north in South Sudan. The king thought of the short man as a god. Ancient Egyptians often used individuals with achondroplasia in their artwork, some dating back to 1500 BC. The painter, Diego Velazquez, did a series of paintings featuring individuals with achondroplasia in the 1600s.


Rome

Roman medical text does not mention restricted growth either, but views were probably similar to those expressed by Aristotle. In the Empire, high society developed a pronounced taste for entertainers with conspicuous physical or mental malformations, such as cretins, hunchbacks, and dwarfs. A few texts mention cages in which pygmies or dwarfs were kept in order to stunt their growth.


Greece

In Greece, the image of dwarfs is also simplified: pathological dwarfs, called vavoi is first described by Aristotle in his treatises on natural sciences and physiology. He seems also to have considered disproportionate dwarfism as the archetype of the condition. In the Parts of Animals, he defines a dwarf as a person who, like a child, is characterized by an abnormally large upper body. This observation is not fully accurate: Aristotle does not mention the curvature of the limbs, the shortening of the arms,or any typical facial features.

He adds in other passages, that their intelligence is not fully developed. The weight of their upper body impairs the working of memory. In a late compilation of Aristotelian treatises, does the author define clearly two types of dwarfs, short disproportionate persons, who "have limbs of children", a large upper body, and short lower limbs; and people "small as a whole".

Who discovered Achondroplasia?

In 1994, Dr. John Wasmuth and his colleagues discovered that a mutation of the fibroblast growth factor receptor-3 (FGFR3) gene on human chromosome 4 causes Achondroplasia.

How is the disorder diagnosed?

Your doctor may diagnose children with achondroplasia during the mother’s pregnant or after the infant is born.


Diagnosing During Pregnancy

Some characteristics of achondroplasia are detectable during an ultrasound. These include hydrocephalus, or an abnormally large head. If your doctor suspects achondroplasia, genetic tests may be ordered. These tests look for the defective FGFR3 gene in a sample of amniotic fluid, which is the fluid that surrounds the fetus in the womb.

Diagnosing After Child’s Birth

Your doctor can diagnose your child by looking at his or her features. The doctor may also order X-rays to measure the length of your infant’s bones. This can help confirm a diagnosis. Blood tests may also be ordered to look for the defective FGFR3 gene.


How does a person receive this disorder?

Achondroplasia (ACH) is caused by a missense mutation in FGFR3 (fibroblast growth factor receptor 3) on chromosome 4p in humans. This nucleotide, # 1138 in exon 10 on chromosome 4, has the highest mutation rate known. In 97% of patients, an adenine replaces the normal guanine at this position (observed in cDNA). 3% have a cytosine instead. Both mutations result in the production of the amino acid arginine instead of glycine. This production of arginine enhances gene function and # of FGFR3 signals released. Mitosis is promoted, but cell differentiation is depressed due to enhancement of gene function.This inhibits proliferation and terminal differentiation, resulting in reduced bone growth.


Signs and Symptoms

People with achondroplasia generally have normal intelligence levels. Their symptoms are instead physical.

At birth, a child with this condition will likely have:

  • a 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 which the ring and middle fingers may also point away from each other

  • a disproportionately large head compared to the body

  • an abnormally large, prominent forehead

  • an underdeveloped area of the face between the forehead and upper jaw

Health problems an infant may have include:

  • decreased muscle tone, which can cause delays in walking and other motor skills

  • apnea, which involves brief periods of slowed breathing or breathing that stops

  • hydrocephalus, or water on the brain

  • spinal stenosis, which is a narrowing of the spinal canal that can compress the spinal cord

Children and adults with achondroplasia may:

  • have difficulty bending their elbows

  • be obese

  • experience recurrent ear infections because of narrow passages in the ears

  • develop bowed legs

  • develop an abnormal curvature of the spine called kyphosis or lordosis

  • develop new or more severe spinal stenosis

Treatments

There’s no cure or specific treatment for achondroplasia. If any complications arise, then your doctor will address those issues. For example, antibiotics are given for ear infections and surgery may be performed in severe cases of spinal stenosis.

Some doctors use growth hormones to increase the growth rate of a child’s bones. However, their long-term effects on height haven’t been determined.

Fun Facts

  • Achondroplasia is a Greek word that means without cartilage formation.

  • People with Achondroplasia usually have normal intelligence.

  • Men's average height is 51.8 inches tall which is about 4 ft. 3.

  • Women's average height is 48.6 inches tall which is about 4 ft.

  • Nine out of ten children with Achondroplasia have normal sized parents.

  • Infants who are homozygous achondroplasia rarely live beyond a few months.

  • The greatest shortening occurs in the bone between the shoulder and elbow (humerus) and the bone between the hip and knee (femur).

  • Achondroplasia is the most common type of dwarfism, affecting up to 80% of all little people.

Bibliography

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"Genetics of Achondroplasia." : Background, Pathophysiology, Epidemiology. N.p., n.d. Web. 16 Dec. 2015. <http://emedicine.medscape.com/article/941280-overview>.

"Achondroplasia: Facts on Treatment and Life Expectancy." MedicineNet. N.p., n.d. Web. 16 Dec. 2015. <http://www.medicinenet.com/achondroplasia/article.htm>.

"Achondroplasia." Healthline. N.p., n.d. Web. 16 Dec. 2015. <http://www.healthline.com/health/achondroplasia#Overview1>.

"Internet Encyclopedia of Philosophy." Internet Encyclopedia of Philosophy. N.p., n.d. Web. 14 Dec. 2015. <http://www.iep.utm.edu/daoism/>.

"Achondroplasia." Genetics Home Reference. N.p., n.d. Web. 16 Dec. 2015. <http://ghr.nlm.nih.gov/condition/achondroplasia>.