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Achondroplasia is a genetic disorder causing disproportionate dwarfism due to the inability to convert cartilage into bone in the ends of long bones. It is caused by a random genetic mutation and can lead to physical problems such as middle ear infections, stooping of the legs, dental problems, and weight issues. Two potentially fatal physical problems are compression of the foramen magnum and hydrocephalus. Genetic testing is available, and most adults with this disorder live and work normally.
Achondroplasia is a genetic disorder that causes disproportionate dwarfism. Literally translated, the word means “without cartilage formation.” However, this is a bit misleading. People with this disorder have normal cartilage in most of their body. The exception to this is the cartilage that grows on the ends of the long bones in the arms and legs. The bodies of people with achondroplasia are unable to convert this cartilage into bone. This makes them disproportionately small in stature.
This condition is caused by a random genetic mutation. Most children born with achondroplasia have average height, non-achondroplastic parents. The gene mutation is an autosomal dominant trait, which means that if someone has the gene mutation they will always find that they have the disorder and be able to pass it on to their children.
People with achondroplasia generally have average intelligence and an average life span. All have larger-than-average heads, large, mid-facial foreheads, and a low nasal bridge with narrow nasal passages. Average height ranges from 4 feet 1 inch (about 1.25 meters) to 4 feet 10 inches (about 1.47 meters) and is largely determined by the natural height of the parents.
There are some physical problems that can be seen in most people with achondroplasia. One of the most common problems, especially with children with achondroplasty, is middle ear infections. Early diagnosis and treatment of middle ear infections can prevent permanent hearing loss.
Another common problem among people with this condition is stooping of the legs caused by the way the long bones in the legs are formed. Doctors often recommend surgical straightening of bent legs to prevent it from damaging the hip and knee joints.
Dental problems are also common in people with achondroplasia. These are caused by the way bones form in the mouth. Most people with this disorder require orthodontic correction.
Because a person’s organs with achondroplasty are average in size, weight issues are common later in life. This needs to be controlled due to the added strain that the extra weight can add to the hips and other joints.
Two potentially fatal physical problems of people with achondroplasia are compression of the foramen magnum and hydrocephalus. The foramen magnum is a hole in the base of the skull where the spinal cord attaches to the brain. In many people with this disorder, this hole is smaller than average and can compress the spinal cord. Also, due to the smaller foramen magnum, it is possible for spinal fluid to back up into the skull causing hydrocephalus, a condition more commonly known as “water on the brain”. Death can occur if the spine is compressed or if spinal fluid cannot flow freely.
Those with the genetic mutation have a 50% chance of having a child with the disease. If two dwarfs with achondroplastics have a child together, they have a 50% chance of having a dwarf child, a 25% chance of having a child of average height, and a 25% chance that the child will have what is commonly referred to as “double dominance achondroplasia”. The latter form is always fatal in infancy. Children born with dual dominance suffer from very small rib cages and severe brain abnormalities.
Genetic testing is now readily available for this condition, since the discovery of the genetic mutation in 1994, and is always recommended when both parents have it. Testing can be conducted through amniocentesis or chronic villain sampling.
Most adults with this disorder live and work just as do those without the condition.
