Skeletal Dysplasia

Skeletal dysplasia is a group of rare genetic conditions that influence how a person’s bones, joints, and cartilage form. Different skeletal dysplasias may affect different parts of the body but most often involve the legs and arms, ribcage, skull, and spine. Skeletal dysplasias present differently from child to child. Some children may be born with complications related to their condition, such as breathing difficulties associated with smaller 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, and 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 can result in short limbs, bowed legs, small chest, spine problems, and a prominent forehead.
• Hypochondroplasia can result in short limbs, including short hands and feet.
• Campomelic dysplasia can present as bowlegs, short limbs, clubfeet, missing or fused ribs, ambiguous genitals, flat facial features, and a prominent forehead.
• Achondrogenesis can result in short limbs, a spine that’s not fully formed, and a 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. 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:

• Shorter arms and legs
• 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 may be accompanied by symptoms in other parts of the body, such as:

• Fluid buildup around the brain (hydrocephalus): In some types of skeletal dysplasia, the bones of the skull can develop in ways that make it harder for fluid around the brain (called cerebrospinal fluid) to drain. When this fluid builds up, it causes increased pressure inside the head, a condition known as hydrocephalus.
• Frequent ear infections and possible hearing loss: Changes in the shape of the skull and facial bones can affect the middle ear and the passages that drain fluid from the ear. This can make children more likely to have fluid behind the eardrum and repeated ear infections. If infections happen often, they can sometimes lead to problems with hearing.

Skeletal dysplasia happens because of changes in genes that guide how bones and cartilage grow. Sometimes these changes are passed down from a child’s parents. Other times, genetic changes happen by chance, without a known cause. It’s important to know that skeletal dysplasia is not the result of anything parents did or didn’t do during pregnancy or childhood.

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.

Your child’s pediatrician may also 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.

Although skeletal dysplasia cannot be cured, there are many supportive measures and some treatments available to help your child stay healthy and thrive. Your child’s care plan will depend on their specific type of skeletal dysplasia, how it affects their body, and their individual needs.

• If your baby has mild skeletal dysplasia, their doctor may recommend giving them time to develop before starting medical and/or surgical 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.

At Boston Children’s Hospital, we see children with skeletal dysplasia in our Skeletal Health Center. Depending on when skeletal dysplasia is diagnosed and its severity, your child’s care team may include orthopedic surgeons, endocrinologists, neurosurgeons, geneticists, social workers, and other experts. Our specialists across the hospital collaborate regularly on rare and complex cases to ensure our patients receive excellent care tailored to their specific needs.