Skeletal dysplasias are a complex group of bone and cartilage disorders that can affect the growth, shape and size of the skeleton. There are hundreds of different types of skeletal dysplasias. Skeletal dysplasia occurs in about one in every 4,000 to 5,000 births.
What Causes Skeletal Dysplasias?
Skeletal dysplasias result from genetic changes that lead to problems with the growth of bone and cartilage that typically occurs as a child develops. Some of these genetic changes are inherited from the parents, but more often the changes are sporadic (not inherited). In the case of sporadic genetic changes, the child is the first in the family to be affected.
How Is Skeletal Dysplasia Diagnosed?
Skeletal dysplasia may be suspected by an ultrasound before birth. However, the exact type of dysplasia can be difficult to diagnose prenatally (before birth). As part of routine prenatal care, many obstetricians do an ultrasound exam around the 20th week of pregnancy. During this exam, the bone structure of the fetus is assessed. If skeletal dysplasia is suspected, the mother may undergo a more detailed or 3D ultrasound examination. This may reveal specific problems of the skeletal system, such as short ribs, absent bones or unusual limb lengths. Further, if a problem is detected on ultrasound, the mother may also undergo a fetal MRI (magnetic resonance imaging) to aid in correctly diagnosing the type of dysplasia. Genetic testing may be recommended to confirm the ultrasound findings. In addition, patients will also be seen by a team of specialists from The Chicago Institute for Fetal Health.
Not all skeletal dysplasias are suspected prenatally. After birth, symptoms that might raise concern for a possible skeletal dysplasia include short stature (height), atypical body proportions, waddling gait (abnormal walking pattern), leg bowing, decreased bone density, and hip or knee pain. When there is a concern for a skeletal dysplasia during infancy or early childhood, your doctor may recommend a set of x-rays called a skeletal survey, which looks at all the bones in the body. These x-rays are then reviewed by a radiologist with expertise in skeletal dysplasias. Genetic testing is also sometimes recommended to further confirm a diagnosis.
What Are the Features of Skeletal Dysplasias?
Some of the more common features may include short stature, length of the limbs and/or size of the chest that is out of proportion, bowing of the legs, and hip problems. Specific symptoms vary between different types of skeletal dysplasias.
Achondroplasia is one of the most common forms of skeletal dysplasia.It leads to short stature (height) and occurs due to specific changes in the DNA instructions for the FGFR3 gene.
These DNA changes lead to product (FGFR3 protein) that doesn’t work properly. It remains activated, or turned “ON”, even when it should be “OFF”. The result is suppression of some types of bone growth, leading to shorter arms and legs.
After the baby is born or if a diagnosis is made during infancy or childhood, parents are encouraged to bring their child to the monthly Skeletal Dysplasia Clinic at Lurie Children's. The program allows families to see a geneticist, genetic counselor and orthopedic surgeon on the same day. This makes it easier for the child to get a thorough evaluation that will guide the management of their disorder. Some children may benefit from surgery or bracing which can greatly improve the quality of life for these children.
What Are the Long-term Effects of Skeletal Dysplasias?
Most skeletal dysplasias cause short stature or dwarfism. The long-term outlook for a child born with skeletal dysplasia depends greatly on the type of dysplasia and whether other medical problems are present. However, not all dysplasias have severe medical problems. For example, most children born with achondroplasia, which is one of the most common types, lead full lives. Additionally, there are many support groups online and in the community that can provide information, help and encouragement to families who have a child with a skeletal dysplasia. Little People of America is one such organization.
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