Achondroplasia

From WikiGenetics

1 Definition
2 Description, Signs and Symptoms
3 Inheritance
4 Diagnosis
5 Treatment and Management
6 Prognosis
7 Resources
8 References

[edit] Definition

An autosomal dominant genetic condition that typically results in the most common type of dwarfism, that occurs in 1 in 25,000 live births.

[edit] Description, Signs and Symptoms

Physical characterizations of achondroplasia are abnormal bone growth that causes short stature, disproportionately short limbs, large head with prominent forehead (frontal bossing), and abnormalities of the midface caused by underdevelopment (hypoplasia) which include cheekbones that are not prominent and low or narrow nasal passageways.

At birth, there is commonly apparent prominence of the mid-to-lower back with a small hump which decreases in size with walking, but a noticeable sway, known as lumbar lordosis, of the lower back region occurs. Lumbar lordosis is typically persistent and the legs are bowed.

[edit] Inheritance

Being a result of an autosomal dominant genetic mutation, only one copy of the gene needs to be present in order for achondroplasia to occur. A parent with achondroplasia has a 50% chance of passing on the gene to their offspring, so there will be a 50% chance that each child will have achondroplasia. Homozygosity (having two copies of the same gene) of this mutation would result in a lethal mutation, thus if two people with achondroplasia have children, there is a 25% chance of the child having a normal phenotype, 50% chance that the child will have achondroplasia, and 25% chance that the child will be homozygous for the mutation and die before or shortly after birth.

[edit] Diagnosis

Diagnosis of achondroplasia is often made before birth with the prenatal ultrasound. The condition can also be diagnosed based on the physical features characteristic with achondroplasia, which are evident at birth, and a skeletal survery by way of X-rays can confirm the diagnosis.

Achondroplasia can even be diagnosed at a molecular level before birth. DNA tests can detect the limited number of DNA changes that are responsible for achondroplasia. This method of prenatal diagnosis is accomplished by examination of cells obtained by chorionic villus sampling (CVS) or amniocentesis. Prenatal diagnosis can be particularly useful for families in which both parents have this condition.

[edit] Treatment and Management

There currently is no treatment for achondroplasia. However, techniques in managing the condition include: monitoring of health conditions, surgery to correct spinal abnormalities such as spinal stenosis, and providing educational support for patients and families.

[edit] Prognosis

Prognosis depends on the severity of the individual’s condition, however, typical outcomes show that people with achondroplasia rarely reach 5 feet in height and intelligence is generally in normal range.