What is Achondroplasia?

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  • Topic: Human height, Dwarfism, Cartilage
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Achondroplasia
Community College of Vermont
Anatomy and Physiology I (BIO-2011-VR01)
Spring 2013
By: Carrie A. Thibault

Achondroplasia, meaning “without cartilage formation” is the medical term given to the most common form of dwarfism in the world. An estimated 1 in 15,000 to 1 in 40,000 births are to infants with achondroplasia. The mutation of the fibroblast growth factor receptor 3 gene (FGFR3) in chromosome 4 was first discovered in 1994 by Dr. John Wasmut of the University of California, Irvine while looking for the genetic link to Huntington’s disease. Although it was not connected to Huntington’s disease, the connection to achondroplasia was undeniable. (Associated Press, 1994) Endochondral ossification is the process by which the cartilage turns into trabecular bone.. In achondroplasia, the mutation of the FGFR3 gene causes an arrest in the long bone growth by stopping the transition of cartilage to bone and causing abnormal cartilage growth. Diagnosis of achondroplasia can be done through genetic testing and radiography. X- rays, ultrasounds and Magnetic Resonance Imaging (MRI) can help determine diagnosis.. Diagnosis can also be done by observing physical characteristics and symptoms that are classically seen in patients with achondroplasia. Rapid diagnosis and symptomatic care of the patient with achondroplasia is the primary focus throughout the lifespan as there is no cure for the disease at this time.

Some of the symptoms of achondroplasia are typical and may indicate the disease early on such as a long narrow trunk, trident hand and hypoplasia of the mid-face. Achondroplasia in infants may be also suspected by a “larger than normal head size and hydrocephaly” (National Library of Medicine, 2013). Patients with achondroplasia are distinct in appearance. Obvious signs are the frontal bossing of the forehead, shortened limbs, short stature, hypotonia and bowed legs. Some joints can be hyperextended past the normal limits such as the knees. Other joints such as the hips and elbows have limited extension and rotation. (Conrad- Stoppler, 2012) Individuals with achondroplasia commonly suffer from fractures due to the nature of the disease. When the bones attempt to heal from the fractures the normal process is interrupted due to the abnormal gene. Instead of a fracture being replaced with a bony matrix of trabeculae that would be seen in a patient without achondroplasia, the bone heals by abnormal cartilage growth. This growth acts as padding between the bones fractured ends. This can cause complications such as reoccurring fractures of the afflicted bone or creating unstable joints in places that there should not be. The average height of a person diagnosed with achondroplasia is about 52 inches in males and 49 inches in females. According to the Guinness Book of World Records, the smallest person alive diagnosed with achondroplasia is Jyoti Amge of Nagpur, India who at 18 years old stands at just 24.7 inches tall. (Barrett, Dan, 2012) While most of the signs and symptoms of achondroplasia do not need medical intervention, there are many complications that need to be addressed promptly.

Complications that may arise in a patient with achondroplasia may be emergent, such as stenosis of the foramen magnum which can cause severe central apnea and death. The opening of the skull would have to be enlarged surgically to make room for the spinal cord and nerves that run through it. Women with achondroplasia characteristically have a smaller pelvis which could result in birthing complications and should plan for a cesarean section. A child with the disease may present with an extra large head which could result in bleeding of the brain during vaginal delivery due to cephalo-pelvic disproportion. Achondroplasia can also cause severe lordosis also called swayback. Patients may also develop a kyphosis or a hump in their thoracic spine and need surgery to relieve spinal stenosis, which...
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