Achondroplasia (cont.)

How is achondroplasia diagnosed?

The diagnosis of achondroplasia can be based on the typical physical features, the hallmarks of achondroplasia, evident at birth. Characteristic features are also seen by radiology (X-ray), ultrasound and other imaging techniques. With ultrasound, the diagnosis can sometimes be strongly suspected before birth.

The molecular diagnosis of achondroplasia before birth is feasible. The limited number of DNA changes responsible for achondroplasia and the ease with which they can be detected provide the basis for a simple method for prenatal diagnosis. In families in which both parents have achondroplasia, prenatal diagnosis may be particularly useful, the aim being to distinguish fatal homozygous achondroplasia from heterozygous achondroplasia (with one copy of the achondroplasia gene) from normal. Diagnosis before birth is accomplished by examining cells obtained by chorionic villus sampling (CVS) or amniocentesis.

What can be done for patients with achondroplasia?

Children and adults with achondroplasia can lead normal lives provided they receive attentive, informed care by their physicians and parents. Considerations in monitoring children with achondroplasia include careful measurements of growth (length/height and weight) and head circumference using curves specially standardized for achondroplasia. Knowledgeable pediatric care and periodic orthopedic and neurologic examinations are critical.

When special problems complicate achondroplasia, prompt and expert intervention is important. For example, the foramen magnum (the large opening under the skull) should be surgically enlarged in cases of severe narrowing (stenosis) and compression of the spinal cord. The back of patients with achondroplasia can develop a marked sway (lordosis) to the lower back while abnormalities in the mid-back may cause a small hump (kyphosis) in infancy and compression of the spinal cord in adolescence. The spinal cord compression can require surgery to decompress it. Orthopedic procedures may be required for lengthening of the limb bones and correction of bowed legs (usually after full growth has been achieved). Surgery (lumbar laminectomy) is also indicated when spinal stenosis (narrowing) causes symptoms, which tends to be evident in young adults.

Disproportion between the brain and the base of the skull can sometimes result in hydrocephalus ("water on the brain") which needs to be promptly detected and treated.

The large head with achondroplasia increases the chance of bleeding within the baby's head during vaginal delivery. This should be taken into account in planning the birth and postnatal care. The brainstem (which contains a center for controlling respiration) may be compressed in achondroplasia and contribute to abnormal breathing.

Pregnant women with achondroplasia should have their babies delivered by cesarean birth.

Middle ear infections are frequent and can lead to mild to moderate hearing loss. Therefore, ear infections should be readily suspected and promptly and fully treated with antibiotics or ear tubes. Dental crowding is also common. Teeth should be straightened and, if necessary, removed to alleviate this problem.

Control of obesity is essential. The child with achondroplasia must not be allowed to become overweight. Adults with achondroplasia should also monitor and control their weight because excess weight aggravates back and joint problems.

Treatment with human growth hormone, which is still considered experimental, has been preliminarily reported to increase the growth rate.

Next: How is achondroplasia inherited? »

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