Achondroplasia
medical conditions

Achondroplasia

Explore the available health information, treatment context, and integrative evidence for Achondroplasia.

Background
  • Achondroplasia, also called achondroplastic dwarfism, is a genetic condition that causes people to be abnormally short. On average, adult males with achondroplasia are about four feet, four inches tall, and adult females are about four feet one inch tall. People with the disorder typically have average-sized trunks with abnormally short arms and legs.
  • People with achondroplasia are abnormally short because their bodies have difficulty converting cartilage into bone, particularly in the long bones. Additional physical characteristics of the disorder typically include an enlarged head (called microcephaly) with a prominent forehead and short fingers.
  • Some cases of achondroplasia are inherited, while others occur when a gene randomly mutates during the development of the egg or sperm. The disorder can affect anyone, regardless of their race, ethnicity, or gender.
  • Achondroplasia is the most common type of short-limbed dwarfism. On average, researchers estimate that it affects one person out of 25,000 births worldwide. Studies suggest that the frequency may range from about one out of 10,000 births in Latin America to about 12 out of 77,000 in Denmark.
  • People with achondroplasia are generally able to live long, healthy lives. However, if a baby inherits two copies of a mutated gene (one from each parent), instead of just one, he/she only lives to be a few months old.
  • There is currently no cure for achondroplasia. Treatment focuses on minimizing complications of the disorder, such as sleep apnea, obesity, and arthritis. Many people with achondroplasia encounter discrimination at some point in their lives. Family support, advocacy groups, and social networks may help people overcome some of the challenges they face as a result of this disorder.
Risk Factors and Causes
  • General: People with achondroplasia are born with a mutated, or abnormal, fibroblast growth factor receptor 3 (FGFR3) gene. Normally, this gene provides the body with instructions on how to make a protein called fibroblast growth factor receptor 3. This protein is involved in the development and maintenance of bone and brain tissue. It limits the amount of bone that is formed from cartilage, especially in the long bones in the arms and legs.
  • Two different mutations, or abnormalities, in the FGFR3 gene cause almost all cases of achondroplasia. Scientists believe that these mutations cause the protein to be overactive. As a result, skeletal development is disrupted and symptoms of achondroplasia develop.
  • Random mutation: About 80% of cases are not inherited. This means most people with achondroplasia have parents who are averaged-sized in terms of height. In these cases, the FGFR3 gene randomly becomes mutated during the development of the egg or sperm.
  • Inheritance: About 20% of cases are inherited, or passed down from parents to their children. Each gene has two variations, called alleles. One allele is inherited from each parent. When achondroplasia is inherited, it is passed down as an autosomal dominant trait. This means that just one copy of the mutated gene in each cell is sufficient to cause the disorder. If one parent has achondroplasia, there is a 50% chance that his/her child will have achondroplasia. If both parents have achondroplasia, there is a 75% chance that their child will have the disorder.
  • If both parents have achondroplasia, there is a 25% chance that child will inherit two copies of the mutated gene (one from each parent). In such cases, the child will only live to be a few months old.
Signs and Symptoms
  • Symptoms of achondroplasia are usually apparent at birth. Newborns may have a bone abnormality, called kyphosis, which occurs when a small bump develops on the mid to lower back. However, this bump starts to go away once the infant starts walking. They may also have decreased muscle tone. As a result, it may take them longer to develop the same motor skills as children of the same age.
  • People with achondroplasia typically have abnormally short arms and legs in proportion to their trunks, which are often narrow. On average, adult males with achondroplasia are about four feet, four inches tall, and adult females are about four feet one inch tall.
  • People with the disorder typically have large heads with prominent foreheads. The middle of the face is usually underdeveloped, the cheekbones lack prominence, the nasal bridge is low, and the nasal passages are narrow.
  • The fingers generally appear short and the middle and ring fingers often diverge, giving the hand a three-pronged appearance.
  • The joints may be looser and more flexible than normal. However, the elbow joints and sometimes the hip joints are limited in their movements.
  • People often walk with a pronounced sway of the lower back (called a lordosis). The legs may also become bowed.
Diagnosis
  • Clinical findings: Achondroplasia can be diagnosed based on the patient's physical features shortly after birth. A doctor examines these features during a physical examination. Medical tests, such as X-rays and other imaging techniques, may also be performed to look at the bones. People that have the characteristic signs and symptoms of the disease are diagnosed. Prenatal genetic testing may also be performed to diagnose the condition in a fetus.
  • Genetic testing: If an ultrasound suggests that a fetus may have achondroplasia, or if one or both parents have the disorder, prenatal testing may be suggested. Depending on the specific type of prenatal test performed, a doctor either takes a sample of the mother's amniotic fluid or tissue from the placenta (called chorionic villis). The sample is then analyzed for the presence of one of the mutated genes that are known to cause achondroplasia.
  • There are risks associated with prenatal testing, including miscarriage. Therefore, patients should talk to their doctors about the potential health risks and benefits before making any health-related decisions.
Complications
  • Arthritis: People with achondroplasia have an increased risk of developing arthritis, which causes pain and inflammation of the joints. This is because the fibroblast growth factor receptor 3 protein is overactive in patients with achondroplasia. This protein is involved in the development and maintenance of bone and brain tissue. When this protein is overactive, it drastically limits the amount of bone that is formed from cartilage, especially in the long bones in the arms and legs.
  • Bowed legs (genu varum): Patients with achondroplasia typically experience a progressive development of bowed legs, called genum varum. This is because achondroplasia affects bone development.
  • Crowded teeth: Patients may have overcrowded teeth. Some people may need to have some of their teeth removed in order to prevent complications, such as tooth decay.
  • Ear infections: Because children with achondroplasia typically have abnormal facial features, they have an increased risk of developing ear infections.
  • Obesity: People with achondroplasia are more likely to be overweight or obese. Being overweight may worsen other symptoms of achondroplasia, such as joint pain and sleep apnea. Being overweight also increases the risk of high blood pressure, heart disease, stroke, diabetes, osteoporosis, and cancer.
  • Pregnancy: Women with achondroplasia may develop breathing problems during pregnancy. Pregnant women with achondroplasia almost always require a Caesarean section (surgical delivery of the baby) because the size and shape of the pelvis does not allow for a vaginal delivery.
  • Sleep apnea: People with achondroplasia have an increased risk of experiencing sleep apnea, a serious condition that occurs when a person stops breathing for short periods of time during sleep. Sleep apnea in achondroplasia patients may be related to midface abnormalities that obstruct the airways during sleep. Obese individuals also have an increased risk of experiencing obstructive sleep apnea because they have excess fat in their upper airways. Because sleep apnea causes individuals to wake up frequently throughout the night, patients are often drowsy during the day.
  • Lumbosacral spinal stenosis: Adults with achondroplasia may experience a narrowing of the channel in the lower spine, called lumbosacral spinal stenosis. Achondroplasia causes defective bone formation and may result in abnormally short and thickened pedicles that reduce the distance across the spinal canal. This condition may worsen if the patient is overweight or obese. Because this puts pressure on the spinal cord, it may cause pain and/or numbness in the legs.
  • Neurological impairment: About 20-50% of children with achondroplasia experience neurological impairment that is caused by stunted growth at the base of the skull and spine. This causes the brain stem and spinal cord to become compressed. As a result, other components of the nervous system, such as the spinal nerve roots and cerebrospinal fluid spaces, may also compress. Neurological problems may include: cervico-medullary myelopathy, hydrocephalus, and spinal cord myelopathy.
Treatment

General: There is currently no cure for achondroplasia. Treatment focuses on minimizing complications of the disorder, such as sleep apnea, obesity, and arthritis. Support groups: Many people with achondroplasia encounter discrimination at some point in their lives. Family support, advocacy groups, and social networks may help people overcome some of the challenges they face as a result of their disorder. For example, the nonprofit organization Little People of America provides people with dwarfism, including achondroplasia, and their families with educational information, social support, and advocacy opportunities. People can also talk to their doctors about local organizations that may offer similar support. Healthy diet and exercise: People with achondroplasia have an increased risk of becoming overweight or obese. Eating a healthy and well-balanced diet may help individuals control their weight. The U.S. government issued a revised food pyramid in 2005 in an effort to help Americans live healthier. The pyramid provides 12 different models, which are based on daily calorie needs, ranging from the 1,000-calorie diets for toddlers to 3,200-calorie diets for teenage boys. Regular exercise may also help individuals control their weight. There are many ways for people to exercise including: gardening, walking, sports, and dancing. Because people with achondroplasia generally have bone and joint problems, patients should talk to their doctors before starting exercise programs. Doctors can help individuals choose safe exercises that fit their levels of strength and endurance. The type of exercise is not as important as a consistent exercise schedule. Most experts agree that burning calories should not be the goal of exercise. Exercise that causes extreme pain or discomfort is considered unhealthy by many experts because it may lead to physical injuries. Changes in the home: Small changes in the home can make everyday tasks less challenging for people with achondroplasia. For instance, purchasing step stools and installing lower handrails on the stairways may be helpful adaptations for a person with achondroplasia. Many companies sell adaptive products, such as size-appropriate furniture, for people with achondroplasia. Surgical procedures: Some people with achondroplasia may require surgery. For instance, if the bones in the legs bow significantly, metal staples may be surgically inserted into the ends of long bones, where bone growth occurs. This helps correct the direction of bone growth. In other cases, metal plates may be inserted after a limb bone is divided and straightened. The metal plates hold the bone in place so it will grow straight. Rods or staples may also be inserted into the spine in order to correct the shape of the back. If the bones in the back are putting pressure on the spinal cord, surgery may be performed to increase the size of the opening in the vertebrae. This helps reduce the pressure on the spinal cord. Limb lengthening: A controversial surgery, called limb lengthening, may also be considered. The goal of this procedure is to add several inches in length to the legs and/or arms. During this procedure, a long bone is divided into two or more sections. These pieces of bone are then separated slightly and metal scaffolding braces the bones together. Pines and screws are frequently adjusted in order to keep a tension between the pieces of bones. This allows the bone to slowly grow back together in a complete and longer bone. Although this procedure is promoted in Europe, it is controversial in the United States. This is because, as with any type of surgery, there are risks, and some people believe that this procedure implies that there is something wrong with being short.

Prevention
  • There is currently no known method of prevention against achondroplasia.
  • Individuals who have achondroplasia may meet with a genetic counselor to learn more about the risks of having a child with the disorder. If one parent has achondroplasia, there is a 50% chance with each birth that a child will inherit the condition. However, most cases of achondroplasia occur randomly and are not inherited.
  • Prenatal screening and diagnostic tests may also be performed to determine if a mother's fetus has achondroplasia. However, there are serious risks associated with prenatal testing, including miscarriage. Therefore, patients should discuss the potential health risks and benefits of prenatal tests before making any health-related decisions.
References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

  1. Carter EM, Davis JG, Raggio CL. Advances in understanding etiology of achondroplasia and review of management. Curr Opin Pediatr. 2007 Feb;19(1):32-7. View Abstract
  2. Horton WA, Hall JG, Hecht JT. Achondroplasia. Lancet. 2007 Jul 14;370(9582):162-72.
  3. Human Growth Foundation.
  4. National Human Genome Research Institute (NHGRI).
  5. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS).
  6. Natural Standard: The Authority on Integrative Medicine. . Copyright © 2008.
  7. Onodera K, Niikuni N, Chigono T, et al. Sleep disordered breathing in children with achondroplasia. Part 2. Relationship with craniofacial and airway morphology. Int J Pediatr Otorhinolaryngol. 2006 Mar;70(3):453-61. Epub 2006 Jan 6. View Abstract
  8. Richette P, Bardin T, Stheneur C. Achondroplasia: from genotype to phenotype. Joint Bone Spine. 2008 Mar;75(2):125-30. Epub 2007 Sep 25. View Abstract
  9. Trotter TL, Hall JG; American Academy of Pediatrics Committee on Genetics. Health supervision for children with achondroplasia. Pediatrics. 2005 Sep;116(3):771-83. View Abstract
  10. Zucconi M, Weber G, Castronovo V, et al. Sleep and upper airway obstruction in children with achondroplasia. J Pediatr. 1996 Nov;129(5):743-9. View Abstract