Skeletal Dysplasia

Skeletal dysplasia is a category of rare genetic disorders that cause abnormal development of a baby’s bones, joints, and cartilage. While skeletal dysplasia affects different parts of the body in different children, the areas most often affected include the legs and arms, ribcage, skull, and spine.

About 1 in 5,000 babies is born with skeletal dysplasia, which varies in severity. Children with mild cases often have short stature and legs and arms that are short compared to the rest of their bodies. Children with more severe skeletal dysplasia may be born with serious complications such as breathing problems caused by small chest cavities.

There are about 400 types of skeletal dysplasia. The descriptions below include some of the more common types of skeletal dysplasia. However, it’s important to keep in mind that many children with skeletal dysplasia experience some — not all — of the related complications.

• Achondroplasia is the most common type of skeletal dysplasia. Possible complications include spinal stenosis, shortened limbs, short fingers, prominent forehead, compression of the lower spine.
• Osteogenesis imperfecta is also known as brittle bone disease. Children with osteogenesis imperfecta have fragile bones that fracture easily. They may also have short stature, bone deformity, osteoporosis, and a soft, thin skull.
• Thanatophoric dysplasia: children may have short limbs, bowed legs, small chest, spine problems, prominent forehead.
• Hypochondroplasia: children may have short limbs, including short hands and feet.
• Campomelic dysplasia: children may have bowlegs, short limbs, clubfeet, missing or fused ribs, ambiguous genitals, flat facial features, prominent forehead.
• Achnodrogenesis: children may have short limbs, spine not fully formed, small chest.

In some children, symptoms of skeletal dysplasia may be visible at birth. In others, the symptoms may appear later, as they grow and develop. Further, because there are so many types and levels of severity, the symptoms of skeletal dysplasia can affect different parts of the body.

Skeletal dysplasia symptoms in the arms and legs

Skeletal dysplasia often causes irregular growth in a child’s arms and legs. A child with skeletal dysplasia may have:

• Short arms and legs compared to the rest of their body
• Stiff or immobile joints, including the fingers, wrists, feet, ankles, and knees
• Hips and other joints that become easily dislocated
• One leg shorter than the other (leg-length discrepancy)
• Legs that bow outward (bowlegs) or inward (knock knees)
• One or both feet that curve inward (clubfoot)

Skeletal dysplasia symptoms in the spine and torso

Skeletal dysplasia can cause problems in the development of the spine, neck, and chest. Complications may include:

• Small chest cavity and missing or fused ribs (thoracic insufficiency syndrome), which can make it hard for a child to breathe
• Extra bone growth in the spinal column that presses against the spinal cord (spinal stenosis)
• Spinal curvatures that grow too large (kyphosis, lordosis), or curve in the wrong direction (scoliosis)
• Cervical spine instability, inability of the neck to support the weight of the head

Skeletal dysplasia symptoms in other parts of the body

Skeletal dysplasia can interfere with the healthy development of other areas of the body. These symptoms can include:

• Large head compared to the rest of the body
• Prominent forehead
• Underdeveloped facial features
• Fluid buildup around the brain (hydrocephalus)
• Frequent ear infections, possibly leading to hearing loss

Skeletal dysplasia is a genetic disorder. Some children inherit the condition from their parents. In other cases, a baby’s genes mutate (change) during pregnancy for no known reason, leading to skeletal dysplasia.

Skeletal dysplasia is often diagnosed during pregnancy by prenatal ultrasound. In general, the earlier skeletal dysplasia becomes detectable on an ultrasound, the more severe it tends to be. If a baby has a family history of skeletal dysplasia, genetic testing can detect the condition.

If not detected before birth, you or your child’s pediatrician may notice signs of skeletal dysplasia during your baby’s first year. In many cases, one of the first signs is that the baby’s head grows much larger than the rest of their body. Your child’s doctor may order one or more imaging tests to confirm the diagnosis and determine its severity:

• X-ray for images of your child’s bone structure
• Computed tomography (CT) scan for more detailed images of your child’s bones and the surrounding tissues
• Magnetic resonance imaging (MRI) for a detailed image of your child’s bones and the surrounding tissues. MRIs take longer but provide more detail than CT scans.

There is no cure for skeletal dysplasia. Your child’s treatment will depend on what type they have, its severity, and what parts of their body are affected.

• If your baby has mild skeletal dysplasia, their doctor may recommend giving them time to develop before starting medical treatment.
• Some treatments focus on making your baby more comfortable and reducing the painful symptoms of skeletal dysplasia.
• Some treatments use medicine to stimulate growth or change the way your child’s bones are growing.
• Some treatments involve surgery to correct bone growth.

Surgical treatments for skeletal dysplasia

• Spinal stenosis surgery can correct spinal stenosis. A neurosurgeon will remove excess bone around the spinal cord, and an orthopedic surgeon will stabilize the spine with screws and rods.
• Spinal fusion surgery can correct scoliosis or kyphosis. An orthopedic surgeon will attach screws and rods to the curved section of your child’s spine to hold the spine in a straighter position. Bone chips will then be placed around the affected vertebrae to stimulate bone growth. Over time, this section of the spine will fuse into solid, stable bone.
• Limb-lengthening surgery can correct a significant leg-length discrepancy or short arms that interfere with daily activities. An orthopedic surgeon will cut the bone to be lengthened and attach a device to the limb. A few days after surgery, the device will be adjusted to pull the two ends of bone apart very gradually, stimulating the growth of new bone. This process is repeated several times over a period of months until the limb reaches its desired length.
• Osteotomy can correct a bone that is growing crooked. An orthopedic surgeon will cut the bone and move it into a straighter position. Screws and metal plates will hold the bone in its new position as it heals.

Depending on when skeletal dysplasia is diagnosed and its severity, your child’s care team may include specialists from our Fetal Care and Surgery Center, Division of Genetics and Genomics, Orthopedics and Sports Medicine Department, Department of Neurosurgery, Division of Endocrinology, and Social Work. Our specialists across the hospital collaborate regularly on rare and complex cases to ensure our patients receive excellent care tailored to their specific needs.

We also collaborate with patient support groups that provide our patients and their families information, support, and other resources. These include Little People of America and the Osteogenesis Imperfecta Foundation. As part of the Skeletal Dysplasia Management Consortium, we contribute to research that helps improve the clinical management of skeletal dysplasia.