Achondroplasia is the most common form of short-limb dwarfism. It is an autosomal dominant disorder caused by a mutation in the gene that creates the cells (fibroblasts) which convert cartilage to bone. This means, if the gene is passed on by one parent, the child will have achondroplasia. However, over 80% of individuals born with this disorder are born to parents who do not have the disorder. It affects mainly the long bones. As a result, individuals who have achondroplasia have short limbs but normal trunk height and head size with a prominent forehead.
During pregnancy, a prenatal ultrasound which shows excess amniotic fluid and abnormal bone length measurements may be suspicious for achondroplasia. However, the diagnosis is usually made through physical examination of the infant after birth and through utilization of x-rays and ultrasound. Characteristic features of an infant with achondroplasia include:
Other signs and symptoms of achondroplasia which may develop over time include:
Although the cause of achondroplasia is known, there is currently no known treatment for the underlying condition itself. Human growth hormone has been used to treat other types of dwarfism but has not proven beneficial for patients with achondroplasia. Overall, most treatment involves prevention and treatment of complications related to achondroplasia.
Children with achondroplasia can lead normal lives provided they receive appropriate care and follow-up by knowledgeable providers. Babies with achondroplasia need to be monitored for problems with too much fluid on the brain (hydrocephalus) and may require a shunt to drain the fluid. Similarly, some babies may need the base of the skull (foramen magnum) to be surgically enlarged to prevent spinal cord compression. It is important children with achondroplasia receive timely dental care to prevent tooth overcrowding. Treating and preventing ear infections to prevent long-term hearing loss is critical. Limb-lengthening is a controversial treatment to increase the overall height and limb length of patients with achondroplasia. Preventing obesity, to reduce joint and back problems, is also important. Some patients may require a laminectomy for spinal stenosis as young adults.
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