What is achondroplasia?
Achondroplasia is the most common cause of bone growth disorder and dwarfism. Although this means “no cartilage formation,” there is a problem with the conversion of cartilage to bone during early development. The biggest effect of this is that the long bones of the arms and legs usually do not grow to the proper length, although there are also problems with the growth of the bones of the skull and face.
Achondroplasia does not affect intelligence, although the brain often expands as a result of the condition. Achondroplasia is a genetic (inherited) condition that causes abnormally short stature and is a common cause of short stature with fewer organs. The average height of an adult with achondroplasia is 131 cm (52 inches or 4 feet 4 inches) in males and 124 cm (49 inches or 4 feet 1 inch) in females.
Although achondroplasia means “no cartilage formation”, the defect of achondroplasia is not in the formation of cartilage but in the conversion of bone, especially in long bones.
- Achondroplasia is a genetic bone growth disorder.
- Achondroplasia is the most common cause of dwarfism (asymmetric dwarfism of small limbs).
- Achondroplasia is the least common cause of short stature.
- A characteristic feature of a person with achondroplasia.
- Intelligence is common in people with this disease.
- Complications of this disease affect the brain and spinal cord.
- Achondroplasia is inherited as a predominant trait, although 80% of cases are caused by new mutations (even the parents do not have achondroplasia).
- It can be diagnosed before birth.
Symptoms of achondroplasia
People with achondroplasia usually have normal levels of intelligence. Its symptoms are physical, not mental. Each child can have different symptoms. Common symptoms can include:
At birth, children with this condition have:
- Arms, legs, and little fingers
- The upper arms and thighs are narrower than the forearms and lower legs.
- Large head with a prominent forehead and flat nasal bridge
- Congestion or poorly formed teeth
The curved spine (lordosis or “backward rolling”), which leads to kyphosis (hump), develops a small bump near the shoulders, which usually disappears after the child begins to walk.
Small vertebral canals (vertebral column or vertebrae) cause compression of the spinal cord in adolescence. A child with this disease can die suddenly during sleep or in infancy from compression of the upper end of the spine, which can interfere with breathing.
- Legs are bent
- Small and spacious flat feet
- Extra space between the middle and ring fingers (also known as a trident hand)
- Poor muscle tone and loose joints
- Short periods of slow or stopped breathing (called apnea)
- Frequent middle ear infections can lead to hearing loss
- Delayed developmental milestones, such as walking (which can occur between 18 and 24 months of the year)
- People with this disease have normal intelligence and life expectancy.
Children and adults with achondroplasia:
- Have trouble bending their elbows
- These have arrears
- You experience recurring ear infections due to narrow canals in your ears.
- Development of bent legs
- Developing an abnormal curve in the spine called kyphosis or lordosis.
- Developing a new or more severe spinal stenosis
The symptoms of this disease appear to be similar to those of other complications or medical conditions.
What causes achondroplasia?
During early fetal development, your skeleton becomes very cartilaginous. In general, most of the cartilage eventually turns into bone. However, if you have this disease, most of the cartilage does not turn into bone. It is caused by mutations in the FGFR3 gene.
The FGFR3 gene directs your body to make the protein necessary for the growth and maintenance of bones. Mutations in the FGFR3 gene make the protein overactive. It interferes with normal skeletal development.
Is achondroplasia inherited?
According to the National Human Genome Research Institute (NHGRI), in more than 80 per cent of cases, it is not inherited. These cases are caused by abnormal mutations in the FGFR3 gene.
- 20 per cent of cases are inherited. The mutation follows the autosomal dominant inheritance pattern.
- Only one parent will have to cross the faulty FGFR3 gene for a child to develop this disease.
- If one of the parents has this condition, the child has a 50 per cent chance of developing it.
If both parents have this condition, the child:
- 25 per cent chance of normal height
- 50 per cent chance of having a defective gene that causes achondroplasia
- There is a 25 per cent chance of inheriting two faulty genes, resulting in a malignant form of achondroplasia called homozygous achondroplasia.
- Babies born with homozygous achondroplasia are usually born or die within a few months of birth.
- If your family has a history of this disease, you may want to have genetic testing done before you get pregnant so that you can fully understand the risks to your future baby’s health.
Diagnosis of achondroplasia
The diagnosis of achondroplasia depends on the general physical symptoms, the symptoms of achondroplasia, which are evident at birth. X-rays, ultrasound, and other imaging techniques also look for characteristic features. With ultrasound, the diagnosis before birth is sometimes strongly suspected.
If there is a suspicion or increased risk of the disease (such as when the parents are affected by this disease), a molecular diagnosis of this disease is possible before birth. In families in which both parents have this disease, prenatal diagnosis is particularly useful, as the goal is to differentiate homozygous malignant achondroplasia (with two copies of the defective gene) from that of achondroplasia (with one copy of the achondroplasia gene). Prenatal diagnosis is made by examining cells obtained by chorionic villus sampling (CVS) or amniocentesis.
Treatment of achondroplasia
Currently, there is no way to prevent or treat achondroplasia, as most cases are caused by new, unexpected mutations. Growth hormone treatment does not significantly affect the height of a person with this disease. In specific cases, surgeries may be considered along the leg.
Although the cause of this disease is known, there is currently no known treatment for the underlying condition itself. Human growth hormone has been used to treat other types of dwarfism but has not proven beneficial for patients with this disease. Overall, most treatment involves the prevention and treatment of complications related to this disease.
It is important to recognize bone abnormalities, especially in the back, to prevent breathing difficulties, leg pain, or major dysfunctions. If the kyphosis (or hump) does not appear when a child begins to walk, it must be corrected surgically. Surgery can also help flex your legs. Ear infections need immediate treatment to avoid the risk of hearing loss. Dental problems must be treated by an orthodontist (a dentist who specializes in dental alignment).
Research on a family of genes called fibroblast growth factors has identified a gene that causes this disease. The goal is to understand how a faulty gene can cause the symptoms found in this disease, leading to better treatment. These genes have been linked to many other inherited skeletal disorders.
It cannot be cured. However, some adverse effects of the condition may require treatment:
- Babies with a curve in the lower spine may need a back brace for about the first year of their life.
- Effect of bowleg achondroplasia. Surgery can fix this.
- The large opening under the skull is very narrow and may need to be surgically widened to avoid compression of the nerves, blood vessels, and spinal cord, resulting in shortness of breath (central apnea) and sudden death.
- Middle ear infections are common and cause some degree of hearing loss, so they must be treated immediately with antibiotics.
- Delays can aggravate back and joint problems, so patients should monitor their weight and seek the advice of their doctor to prevent obesity.
- Patients can live normal and full lives, but due to the number of complications of their condition, it is important that they seek careful care from their parents and doctors who are familiar with the condition. Children with the condition need regular checkups with measurements to monitor their growth.
What type of specialist treats achondroplasia?
Paediatricians often guide paediatricians in treating a variety of problems, from orthopaedic surgeons to neurosurgeons.