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Achondroplasia

What is Achondroplasia?

Achondroplasia is the most frequent type of short limb dwarfism. It is a disorder that prevents the changing of cartilage to bone, leading to short arms and legs, limited range of elbow motion, and enlarged head. In almost all individuals, the disorder results from a spontaneous change in genetic material that leads to an autosomal dominant trait.

 

Achondroplasia is the most frequent type of short limb dwarfism. It is a disorder that prevents the changing of cartilage to bone, leading to short arms and legs, limited range of elbow motion, and enlarged head. In almost all individuals, the disorder results from a spontaneous change in genetic material that leads to an autosomal dominant trait.

Special thanks to: 

Writer: Dorsa Kord, Research Associate, RareShare

Reviewer: Dr. Morrys Kaisermann, Clinical Research manager, GlaxoSmithKline, Brazil

Achondroplasia is the most common type of dwarfism. It appears to affect males and females in relatively equal numbers.  The condition occurs in 1/15,000-40,000 births worldwide.

Synonyms for Achondroplasia has not been added yet.

Achondroplasia is caused by a mutation in the gene fibroblast growth factor receptor 3 (FGFR3), on chromosome 4. This gene regulates development and maintenance of bone tissue. The mutated gene generates malfunctioning proteins that consequently results in severely shortened bones. Inheritance is autosomal dominant, meaning one copy of the altered gene is sufficient to cause the disorder. If two mutated genes are inherited, achondroplasia is fatal.

Achondroplasia is characterized by long narrow trunks and short limbs. Affected individuals have enlarged head, with a prominent forehead, and a flat depressed nasal bridge. Hands are usually in a trident formation, or three-pronged position during extension. Compression of the brain stem may occur in some children with achondroplasia resulting in accumulation of fluids in brain and consequently, abnormally large heads. The spine may be excessively curved, either inwards or outwards.  One of the serious complications of the disorder is that the spinal canal may narrow and compress the upper parts of the spinal cord and the brain stem in some individuals, which can result in pain, tangling and weakness in the legs. Legs might also be bowed. Adults reach a height of 131±5.6 cm (men) and 124±5.9 cm (women). Other health problem associated with achondroplasia include obesity, recurrent ear infection, and apnea.

Because this disorder has distinctive physical characteristics, it is easy to identify clinically and radiologically at birth. There are a limited number of mutations related to achondroplasia and they are easily detectable, providing a simple method for prenatal diagnosis. A definitive in utero diagnosis may be difficult to come by as there are other forms of dwarfism and babies may just be small.

One polymerase chain reaction (PCR) and one restriction digest, also known as DNA fragmentation, is adequate to diagnose this condition prenatally. Skeletal survey (a series of X-rays that cover all bones in the body) shows shortened limbs, metaphyseal enlargement, narrowing of the distance between vertebral pedicles in a particular section of the vertebrae (lumbar vertebrae), and an abnormal hip bone with small square iliac wings. Presence of FGFR3 mutation can be tested by molecular genetic testing.  It is also possible to determine if the genetic test is present in the embryo using a screening method called PGD in specialized laboratories.

It is possible to manage achondroplasia through multidisciplinary care. Orthopedic surgery such as surgical lengthening of the limbs, and surgical correction of bowed legs physical therapy can be helpful to affected individuals. Infants may require surgical enlargement of foramen magnum to relieve pressure from brain stem, while adults may require lumbar laminectomy to relieve pressure from lower sections of the spinal cord. It is important to control weight, to prevent obesity from early childhood. Ear infections also need to be treated and an assessment of potential hearing loss is required. Weight loss can also help treat obstructive sleep apnea. Surgical removal of tonsils and adenoids, and/or continuous positive airway pressure can also be beneficial to treat sleep apnea. Growth development curves and health surveillance guidelines for medical issues in achondroplasia are available and may help to follow up the kid’s growth and health status, as well prevent common complications. This includes recommendations for further testing, such as brain and spine CT, MRI, somatosensory evoked potentials and polysomnography for sleep apnea.

Life expectancy of individuals with achondroplasia is only slightly decreased relative to the general population, due to increased risk of cardiovascular disease.

Affected individuals should avoid activities that increase the risk of craniocervical junction injuries. In addition, weight control is essential for people with Achondroplasia. Obesity can worsen the joint and back problems caused by the disorder.

Name Description
Activities which lead to a risk of injury to the craniocervical junction should be avoided .

Achondroplasia. National Institute of Health. https://www.genome.gov/19517823. Updated May 11, 2012. Accessed November 15, 2015.

Achondroplasia. National Organization for Rare Disorders (NORD). http://rarediseases.org/rare-diseases/achondroplasia. Updated 2007, Accessed November 15, 2015.

Defendi, G. Medscape. http://emedicine.medscape.com/article/941280-overview. Updated January 28, 2016. Accessed November 16, 2015.

Manner, P. Managing Pain With Medications After Orthopaedic Surgery. Ortho Info. http://orthoinfo.aaos.org/topic.cfm?topic=A00650. Updated October2011, Accessed February 5, 2016.

Mudgal, P. Skeletal survey. Radiopaedia. http://radiopaedia.org/articles/skeletal-survey. Accesses February 5, 2016. Stöppler, M. Achondroplasia. MedicineNet. http://www.medicinenet.com/achondroplasia/article.htm. Updated November 5, 2015. Accessed November 15, 2015.

Neil K. Kaneshiro. Leg lengthening and shortening. University of Maryland medical center. https://umm.edu/health/medical/ency/articles/leg-lengthening-and-shortening. Updated November 20, 2014. Accessed February 5, 2016.

Any current Treatments?? Created by memathar
Last updated 18 Jun 2010, 01:08 PM

Posted by memathar
18 Jun 2010, 01:08 PM

My 4 week old nephew has just been diagnosed with Achondroplasia and I would like to know if anyone knows about a possible treatment we could follow. Thank you

Addressing Achondroplasia Created by Pokey_Luv
Last updated 4 May 2009, 09:53 AM

Posted by Pokey_Luv
4 May 2009, 09:44 AM

I know that some international countries (e.g. Russia) address Achondroplasia with height increase surgery. I found it on this website http://www.ilizarovheightincrease.com. This approach is actually starting to become more common in the US, although very expensive if done here.

Welcome Created by biotechguy
Last updated 29 May 2008, 08:41 PM

Posted by biotechguy
29 May 2008, 08:41 PM

Welcome to the achondroplasia discussion forum

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Any current Treatments??

Created by memathar | Last updated 18 Jun 2010, 01:08 PM

Addressing Achondroplasia

Created by Pokey_Luv | Last updated 4 May 2009, 09:53 AM

Welcome

Created by biotechguy | Last updated 29 May 2008, 08:41 PM


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