Achondroplasia

Specialty of Paediatrics

What is achondroplasia?

Achondroplasia is a bone growth disorder and the most common cause of dwarfism. Although it literally means “without cartilage formation”, the problem is actually in turning the cartilage into bone during early development. The biggest effect of this is that the usually long bones in the arms and legs do not grow to their proper length, although there are usually also problems in how the bones of the skull and face grow as well.

Achondroplasia does not seem to affect intelligence, although the brain is often enlarged as a result of the condition.

Symptoms of achondroplasia

Achondroplasia can be diagnosed at birth from the appearance of the baby:

  • Relatively long torso with disproportionately short arms and legs – the arm and leg bones closest to the torso are the most affected.
  • Large head with prominent forehead
  • Lack of prominence in cheekbones/underdevelopment of the midface (hypoplasia)
  • Short fingers
  • Joint flexibility may be unusual – some joints may extend past their usual stopping points, while others may be limited.
  • Some infants have an abnormal curve or bump in the lower spine

As the child grows, other effects of achondroplasia may be observed:

  • Due to the proportionally large head, the child may reach motor developmental milestones later than children without the condition
  • Hypotonia – decrease in muscle tone
  • Short stature

When fully grown, the most obvious symptom of achondroplasia is dwarfism – most patients are around four feet in height when they reach adulthood.

Medical tests to diagnose achondroplasia

It is usually possible to diagnose achondroplasia at birth, and sometimes even earlier via ultrasound scans. X-rays may be taken to verify the short bones in the limbs.

What are the causes of achondroplasia?

Achondroplasia is a genetic condition. It is an autosomal dominant trait, so only one copy of the gene is needed from one parent for the condition to manifest in the child. However, most cases of achondroplasia are not inherited; rather the vast majority of cases happen due to a spontaneous mutation in the sperm or ovum of one of the parents, neither of whom have the condition.

Treatments for achondroplasia (include types – ASK DOCTORS)

Achondroplasia cannot be cured. However, treatment may be necessary for some of the negative effects of the condition:

  • Infants with a curve in their lower spine may need a back brace for the first year or so of their lives.
  • Bow-leggedness can be an effect of achondroplasia. Surgery may be able to fix this.
  • The large opening under the skull can undergo severe narrowing, and may need to be surgically widened to prevent compression of the nerves, blood vessels, and spinal cord, which can lead to loss of breathing control (central apnoea) and potential sudden death.
  • Middle ear infections are common and can cause some degree of hearing loss, so should be treated promptly with antibiotics.
  • Obesity can worsen back and joint problems, so patients with achondroplasia must control their weight and should take their doctor¡s advice to prevent obesity.

Patients with achondroplasia can live normal and full lives, but due to the number of complications of their condition, it is important that they receive attentive care from both their parents and doctors who are familiar with the condition. Children with the condition will need regular check-ups with measurements taken to monitor their growth.

Which type of specialist treats achondroplasia?

Paediatric specialists will often be responsible for guiding the patient’s treatment through childhood, although a number of different specialists may be responsible for treating the various complications, ranging from orthopaedic surgeons to neurosurgeons.

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