Skeletal dysplasia is the medical term for what most people refer to as “dwarfism”. The term is an umbrella for a group of hundreds of conditions affecting bone and cartilage growth. A child born with skeletal dysplasia will have abnormal differences in the size and shape of their legs, arms, trunk, or skull. He or she may be very short in stature. Additionally, he or she may also have arms and legs that are not in proportion with the rest of the body.
Skeletal dysplasia is a genetic condition. A change or defect in a specific gene, called a mutation, causes the problems in growth. As a whole, skeletal dysplasia is an uncommon condition. It affects about one in every 4,000 births (Lurie).
Skeletal dysplasia is an inherited condition. It is caused by many different types of genetic mutations. An inherited disorder implies that a child is born with the condition. The genetic defect is passed down from parents to children through their genes. These mutations prevent the bones from growing in a normal way. The disease runs in families but can often appear without a family history of skeletal dysplasia (Cedars-Sinai).
The exact genetic defect a person with the condition has is sometimes difficult to determine. The most common type of skeletal dysplasia is called achondroplasia. This is caused by mutations in the FGFR3 gene. Most of the time, the parents of a child born with achondroplasia are of normal height and stature (Unger, 2002).
Other common types of skeletal dysplasia include:
- thanatophoric dysplasia: results in extra folds of skin on the arms and legs, as well as extremely short limbs
- hypochondroplasia: affects conversion of cartilage into bone, resulting in short arms and legs, as well as short, broad hands and feet
- campomelic dysplasia: often fatal in the newborn period, this disorder causes dangerous bowing of the long bones in the legs and often the arms as well
- osteogenesis imperfecta: a disorder that results in fragile bones that break easily
- achondrogenesis: a type of disorder that affects the development of bones and cartilage, resulting in skeletal abnormalities including short limbs and a small body (CHOP)
Specific symptoms of skeletal dysplasia vary with each type. In general, people with the condition have arms, legs, trunk, and a skull of unusual shape and size. Other symptoms include:
Sometimes a child with skeletal dysplasia will be born with a short stature. In other cases, the child will be born with a normal birth length and fail to grow later on. A child’s parent or pediatrician may first discover the dysplasia when they notice that the child’s head is growing out of proportion to the rest of the body.
A doctor may first conduct a physical examination. He or she will measure the child’s height, weight, and head circumference. The lower and upper segments of the body are measured separately to determine proportion. The doctor will also ask for a thorough family and patient history.
Types of skeletal dysplasia are generally classified by which parts of the skeleton are involved (Unger, 2002). X-rays and imaging techniques, such as magnetic resonance imaging (MRI) or computed tomography (CT) may be used by a doctor to identify and assess deformities in bones more accurately. Genetic analysis and molecular analysis may be performed to identify the type of skeletal dysplasia. They can also identify the exact gene mutation causing the condition.
It is sometimes possible to diagnose skeletal dysplasia prior to birth with an ultrasound examination. An ultrasound is a routine exam done by a doctor during a woman’s pregnancy. A doctor may notice abnormal bone structure or limb lengths during the examination. A more detailed ultrasound may be conducted to help diagnose the dysplasia. The exact type of dysplasia is often difficult to diagnose until after birth occurs.
Often a team of doctors from many specialties reviews each individual case of skeletal dysplasia before deciding on a treatment plan. This may involve neurosurgeons, orthopedists, ophthalmologists, endocrinologists, radiologists, geneticists, neurologists, and other doctors. If the bones are constricting the spinal cord or brain stem, for example, a pediatric neurosurgeon may remove the bone or bones causing the problem. The spine will then be supported with metal rods (Johns Hopkins).
Some children may be given growth hormones to help boost growth. This type of treatment involves injections with needles every day. The hormone treatment can help increase height, but many children will probably still remain below normal adult height even with treatment. Surgery to lengthen the limbs may also be used to induce bone growth. However, there are many complications in this type of surgery. It may involve multiple procedures and usually has a long recovery period.
The long-term outlook for children born with skeletal dysplasia greatly depends on the type of dysplasia. According to the Ann & Robert H. Lurie Children’s Hospital of Chicago, about a quarter of fetuses with a skeletal dysplasia will not be born alive (stillborn). About 30 percent will die in the first six weeks after birth. However, many children will live normal lives with normal intelligence and life expectancy (Lurie).