What is Skeletal Dysplasia?
Skeletal dysplasia is a general term that covers multiple conditions affecting bone and cartilage. People with skeletal dysplasia are short in stature, with different sizes and shapes of legs, arms, trunk and skull.
This genetic condition, often referred to as “dwarfism,” results from changes or defects (mutations) in one or more specific genes involved in growth. More than 350 different disorders of the skeleton fall under skeletal dysplasia, and have a wide range of clinical characteristics, ranging from quite mild to severe and even lethal. Some types affect bone development and growth while others also affect mineralization (bone hardening). Approximately half of affected fetuses are either stillborn (23%) or expire during the first six weeks of life (32%). Skeletal dysplasias are usually lethal due to the underdevelopment of the fetal ribs/chest, leading to underdeveloped fetal lungs (pulmonary hypoplasia). The most severe (lethal) skeletal dysplasias are Thanatophoric dysplasia and achondrogenesis. Achondroplasia is the most common non-lethal skeletal dysplasia.
Skeletal dysplasia occurs in about one of every 4,000 births.
How is it diagnosed?
Evaluation of the fetal skeleton is part of the first trimester ultrasound exam conducted around week 12 of pregnancy. Many skeletal dysplasias, especially the lethal ones, may be diagnosed or suspected at the first ultrasound exam, but a follow up ultrasound may be necessary to evaluate whether the fetal bones are growing. The routine 20 week anatomy ultrasound is another time the fetal skeleton is evaluated, and many of the less severe (non-lethal) dysplasias may be suspected or diagnosed at this time. However, many skeletal dysplasias, including achondroplasia, may not become evident until later in the pregnancy.
Because there are literally hundreds of variations of skeletal dysplasia, a precise diagnosis can be made only about 65 percent of the time during pregnancy. However, our team of Maternal-Fetal Medicine Specialists are highly experienced and usually able to diagnose the lethal skeletal dyplasias during the first half of pregnancy. In less severe skeletal dysplasias, a more accurate diagnosis about which type of dysplasia it is may be determined after birth when our team of specialists can examine the baby’s appearance, growth pattern, X-rays, and genetic testing.
If skeletal dysplasia is suspected during pregnancy, the mother may have a more detailed ultrasound exams, which can show abnormalities such as missing or fractured bones and short limbs. You will also meet with one of our Genetic Counselors and Maternal-Fetal Medicine physicians. In some cases, the physician may suggest a magnetic resonance imaging (MRI) study using techniques calibrated for fetus safety. Other tests intended to identify genetic markers associated with skeletal dysplasia may be suggested, including parental testing, chorionic villus sampling or amniocentesis.
How is skeletal dysplasia treated?
The Fetal to Newborn Care Center’s team of specialists reviews each case of skeletal dysplasia to determine an individualized treatment plan. Prenatal consultations with orthopedics, genetics, neonatology, and others will be arranged as necessary. A nurse navigator helps to coordinate care and answer any questions from the family as the pregnancy continues.
Treatment is determined by the type of dysplasia, other medical concerns, and the age of the infant. Unfortunately, up to half of babies with skeletal dysplasia will be stillborn or die within the first six weeks of life. If a lethal skeletal dysplasia is diagnosed, our team of specialists will work closely with the family to develop a personal and custom plan for prenatal care, delivery, and making the most of their time with their infant after birth.
Many children survive and lead relatively normal lives without serious medical problems. In certain types of skeletal dysplasia there are therapies that can be utilized to treat some of the effects. Children may be given growth hormone injections or undergo surgical procedures to lengthen limbs. Whatever treatment your baby requires, you will be guided by our team and provided the best care possible.