Achondroplasia is a type of dwarfism caused by inheritance of a mutated gene, or direct mutation of a gene. Since the cartilage fails to form properly, the bones cannot grow as they normally would. This results in failure of the bones to reach normal adult size. Most with Achondroplasia reach a height of about four feet (1.21 m) at adulthood.
Achondroplasia is called an autosomal dominant condition, because people need inherit only one gene mutation in order to cause the condition. Thus one parent with this disorder has a 50% chance of passing on the gene to each child. Inheriting two genes for it is fatal.
If both parents have the disorder, they have a 25% chance of passing on two of the mutated genes to each child. Two inherited genes for this condition are usually not survivable. Sadly, children who inherit two mutated genes die at birth or shortly thereafter.
Even though Achondroplasia is considered autosomal dominant, there are some people who are born with the condition to parents without outward signs of dwarfism. They clearly don’t have the gene, because carrying the gene would mean they would have the condition. Thus in rare cases, the gene may mutate on its own and create the condition. Studies have shown this to be linked to mutations of the sperm cells from the father. Such mutations become more common as men age.
Still the condition is not exactly common. It is present in all races in about 1 in 20,000 to 40,000 births. That is .005% - .0025% of the general population. It remains a difficult, but relatively rare condition.
Generally, Achondroplasia can be diagnosed in utero through genetics testing early in the pregnancy, since the gene responsible has been identified. Further, ultrasound in the second half of a pregnancy shows signs of the disorder. In particular, length of the femur does not accord with its width as the pregnancy progresses.
Diagnosis after birth is made through physical exam and x-ray, which shows developmental problems with many of the bones. The achondroplasic adult can be recognized by his or her short stature, bowing of the legs, relatively large head but small nose, curvature of the spine, and short fingers and toes. Although the condition often brings unwanted comments from insensitive people, it is not usually life threatening.
There are a few complications common to those with Achondroplasia. They may have slightly delayed development as children, and are quite prone to ear infections. Some children have an increased risk for developing hydrocephalus, or water on the brain. Aside from these complications, which are present in many without the disorder, it usually results in the same life span as those without the gene.
Recently doctors have begun attempting surgery and/or medication to help those with Achondroplasia achieve greater height. These surgeries include bone-lengthening surgeries, which break the bone and then stimulate regrowth in order to attain taller stature. Further, some physicians are experimenting with the use of human growth hormone on those with the condition to attempt greater growing potential. These studies are still in their infancy.
Some with dwarfism protest these interventions and criticize doctors, especially, for bone lengthening surgeries. These surgeries typically are quite painful for children for long periods of time. People with this form of dwarfism may argue that since the condition is not life threatening, these surgeries are merely cosmetic and inflict unnecessary pain on a child. Conversely, some parents feel the physical pain of surgeries may save children from experiencing the emotional pain of criticism by peer groups.