Achondroplasia is the most common type of rare genetic bone disorder. The strong, flexible tissue called cartilage is not made into bone as normal. This causes a series of signs, such as short arms and legs and a large head. This condition used to be called dwarfism. A boy with the condition will reach an average adult height of about 4 feet, 4 inches (52 inches). A girl with the condition will reach an average adult height of about 4 feet, 1 inch (49 inches). People with achondroplasia have normal intelligence and normal lifespan.
Achondroplasia is a genetic disease. It is an autosomal dominant disease. This means that only one abnormal gene inherited from one parent leads to the condition. Most cases of achondroplasia are from a new gene mutation in families. This means the parents are average height and do not have the abnormal gene.
Having a parent with achondroplasia increases the risk of being born with the condition. But most babies born with the condition do not have a family history of it.
Signs can occur a bit differently in each child. They can include:
- Large head size with large forehead
- Flattened bridge of nose
- Crowded or crooked teeth
- Short arms, legs, and fingers, but normal-sized torso
- Upper arms and thighs more shortened
- Bowed lower legs
- Curved lower spine (lordosis or swayback), which may lead to hunchback (kyphosis)
- A small hump near the shoulders that usually goes away after a child begins walking
- Flat feet that are short and broad
- Extra space between the middle and ring fingers (trident hand)
- Poor muscle tone and loose joints
- Short spells of slow or stopped breathing (apnea)
- Middle ear infections that occur often, which may lead to hearing loss
- Delayed development milestones, such as walking occurring at 18 to 24 months instead of at 12 months
- Small canals in the spinal bones that can cause breathing problems
The signs of achondroplasia can be like other health conditions. Make sure your child sees their healthcare provider for a diagnosis.
Achondroplasia can be diagnosed before birth by fetal ultrasound. This test uses sound waves and a computer to create images of the baby growing in the womb. DNA testing can also be done before birth to confirm fetal ultrasound results.
The condition can also be diagnosed after birth with a physical exam. You can track your child's growth for any signs of slowing. In particular, note if it's different from how your other children grew.
There is no treatment for changing the condition. But different kinds of treatment can be done to help relieve problems caused by the condition.
Surgery may be done to:
- Treat hunchback (kyphosis)
- Lengthen the legs, in some cases
- Treat bowing of the legs
Other treatments may include:
- Fixing dental problems. A child may need to be treated by an orthodontist. This is a dentist with special training in fixing the alignment of teeth.
- Treating ear infections right away. This is to avoid the risk of hearing loss.
- Follow-up appointments to look for bone problems. The spine needs to be checked to prevent breathing problems. Breathing problems can happen if the upper end of the spine is compressed. Other bones need to be checked to prevent leg pain or loss of function.
Treatment with growth hormone does not largely affect the height of a person with achondroplasia. Studies are being done to see if other growth factors such as hormone medicine or treatment may help. Treatment focuses on dealing with the problems caused by the condition.
Health problems are common in children and adults with achondroplasia. Not all of the below problems occur in every child with achondroplasia. Each problem can be addressed by your child's healthcare team. Problems may include:
- No breathing for short periods of time (apnea). Babies often have episodes of apnea. Surgery to remove the tonsils and adenoids often corrects this problem.
- Regular ear infections. These may need to be treated with ear tubes.
- Buildup of fluid in the brain (hydrocephalus). This may need to be drained or managed with the insertion of a tube called a shunt.
- Posture problems. Babies may have a small hump in the upper back (kyphosis). This often goes away when a child begins to walk. But walking often leads to the lower back curving inward (lordosis). Physical therapy may help with this problem.
- Dental problems. Crowded or crooked teeth may need to be treated by an orthodontist.
- Obesity. Your child’s healthcare provider can advise ways to help keep your child’s weight healthy.
A child with the condition may also have small vertebral canals. These are the spaces inside the spinal bones. This may lead to spinal cord compression as a child gets older. In rare cases, a child with achondroplasia may die suddenly in infancy or early childhood during sleep because of compression of the upper end of the spinal cord. Compression in this area causes problems with breathing. Around 12 months of age, your child's healthcare provider may recommend a CT scan or MRI scan to check the diameter of the spinal canal to help prevent this complication.
Most cases occur in families with no history of the condition and can't be prevented. If a parent or parents have achondroplasia, a genetic counselor can give you information about the possibility of passing the condition on to your child.
It is important to keep all well-child appointments so your child's health can be regularly monitored. Keep an ongoing list of questions and bring them with you to your child's appointments. Living with achondroplasia means adapting to being short in a world built mostly for taller people. It also means watching for possible complications and managing problems that occur. A healthcare team that has worked with the condition can help you manage your child's physical and emotional needs. Groups such as Little People of America and Magic Foundation can give support and information to your family and your child.
Your child will also have special protection in the public education system. The Americans with Disabilities Act and Section 504 of the Rehabilitation Act of 1973 provide these protections. Review the online resources and check with your state or local school board about when and how to ask for classroom and other school changes your child may need. You will become your child's most important supporter in the school system.
When to Call a Healthcare Provider
If your child has achondroplasia, call the healthcare provider if your child has:
- Back pain
- Tingling or weakness in the arms or legs
- Trouble breathing
- New symptoms or symptoms that get worse
- Achondroplasia is a type of rare genetic bone disorder. The strong, flexible tissue called cartilage is not made into bone as normal.
- People with achondroplasia have normal intelligence and normal lifespan.
- Achondroplasia is a genetic disease. Most cases of achondroplasia are from a new gene mutation in families. This means the parents are average height and do not have the abnormal gene.
- Signs can include short arms and legs, large head, and flattened bridge of nose.
- Achondroplasia can be diagnosed before birth by fetal ultrasound.
- Different kinds of treatment can be done to help relieve problems caused by the condition.
- Living with achondroplasia means watching for possible complications and managing problems that occur.
- Federal laws protect your child's right to a free and appropriate public education.
- Groups such as Little People of America and the Magic Foundation can give support and information to your family and your child.
Tips to help you get the most from a visit to your child’s healthcare provider:
- Know the reason for the visit and what you want to happen.
- Before your visit, write down questions you want answered.
- At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you for your child.
- Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.
- Ask if your child’s condition can be treated in other ways.
- Know why a test or procedure is recommended and what the results could mean.
- Know what to expect if your child does not take the medicine or have the test or procedure.
- If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
- Know how you can contact your child’s provider after office hours. This is important if your child becomes ill and you have questions or need advice.