Chromosomal and Genetic Conditions

Dwarfism and Skeletal Dysplasias

What are dwarfism and skeletal dysplasias?

Note the short proximal limb segments with preservation of trunk length. Courtesy of 'Practice of Pediatric Orthopedics,' ©2001 Lippincott Williams and Wilkins

People with achondroplasia may have short upper arms and upper legs compared with the length of their trunk.

Skeletal dysplasias are a group of more than 300 disorders in which a child’s bones do not grow the way bones usually do. Often, children who have skeletal dysplasias are very short.

Dwarfism is a type of short stature that happens when the bones do not have the ability to grow to an average length. Instead, they are short and sometimes crooked. The child’s arms and legs may be short compared with the rest of the body. Or the child’s trunk may be short compared with the rest of the body. The most common type of dwarfism is called achondroplasia.

  • Skeletal dysplasias affect 1 in 5,000 children. Achondroplasia is less common and affects 1 in 15,000 children.

  • Most skeletal dysplasia is caused by a defective gene that stops bone from growing in the usual way. Sometimes this gene is passed on from a parent to a child (genetic). Much more often, though, the condition arises from a new random change in a gene (spontaneous genetic mutation), and the baby is the first in the family to be affected.

  • Children can be shorter than others their age for many reasons but not have any form of skeletal dysplasia. They may have:

    • Short parents
    • A lack of the hormones that help control growth
    • A disease that affects the kidneys, heart or intestines
    • A problem with nutrition or digestion that stops calcium and vitamin D from working properly in their bodies and promoting growth

Dwarfism and skeletal dysplasias at Seattle Children’s

Seattle Children’s Skeletal Health Program specializes in diagnosing and caring for infants, children, adolescents and some adults with dwarfism, other types of skeletal dysplasias and metabolic bone diseases. We see many children each year with these conditions.

Our goals are to:

  • Accurately identify your child’s condition
  • Understand all the ways your child is affected
  • Help you learn what to expect throughout your child’s life, from birth to adulthood
  • Provide comprehensive, expert care
  • The Skeletal Health Program brings together orthopedic doctors, endocrinologists, pulmonologists, geneticists, radiologists, nurses and nurse practitioners to care for your child.

    Our doctors and nurses have a great deal of experience and are known internationally for their expertise in dwarfism and skeletal dysplasias. We have also written widely on the subject and are active with Little People of America, Inc., the advocacy and support group for families with dwarfism, and Camp Korey, which offers camps for children with skeletal dysplasia and metabolic bone diseases.

  • Based on your child’s needs, the Skeletal Health Program team will involve specialists from other areas of Seattle Children’s, like Neurosurgery, Pulmonary and Sleep Medicine, Otolaryngology, Audiology, the Heart Center and Dentistry, as well as social services. Experts in our Spine Program treat spine problems linked with dwarfism and skeletal dysplasias.

  • For some families, our work begins even before their baby is born. If a pregnant woman’s ultrasound suggests that her developing baby may have a skeletal dysplasia, we work with Seattle Children’s Prenatal Diagnosis and Treatment Program to provide diagnostic and counseling services to her and her family.

    After birth, we tailor care to your child’s age and developmental stage, always with a focus on their long-term health and wellness.

    The Skeletal Health Program also provides evaluation, genetic counseling, prenatal consultation and medical management for adults with dwarfism and rare bone conditions. If adult patients need surgery, we work with surgeons from UW Medicine.

  • Our team has done research to expand medical knowledge about dwarfism and skeletal dysplasias and to improve care and quality of life for patients everywhere. Recently Seattle Children’s doctors helped to found the Skeletal Dysplasia Management Consortium, an international panel of experts that developed evidence-based guidelines for diagnosing and treating skeletal dysplasias. Learn more about current orthopedics research at Seattle Children’s.

Symptoms of dwarfism and skeletal dysplasias

Children with dwarfism are very far below average height for their age. They may not have full motion in their joints, and they sometimes have bowlegs or knock-knees. Often, their arms, legs or trunk are short compared with the rest of the body.

Diagnosis of dwarfism and skeletal dysplasias

Children usually come to us after their parents or doctors notice:

  • They are not growing as quickly as other children their age.
  • Their arms and legs, trunk or face look different from other children’s.
  • They develop scoliosis before age 10.
  • They break their bones more often than other children.
  • When you come to our clinic, we ask about your child’s growth history. We also ask about the height of members of your child’s family and how the mother’s pregnancy went.

    We will want to know about any medical conditions your child has and any similar problems in the rest of your family.

  • Next, we examine your child. We measure their height and the length of their arms and legs. We take X-rays of their arms, legs, pelvis, spine and skull. This is called a skeletal survey. It helps us find out which bones may not be growing the way they usually do in children.

    • Blood tests. We may take blood samples from your child to test for levels of hormones and other chemicals that can help us understand how your child is growing.
    • MRI or CT scan. Because children may have other conditions that come along with skeletal dysplasias, we may ask your child to have an MRI (magnetic resonance imaging) scan or a CT (computed tomography) scan to check for other problems.
    • Sleep study. Often children with dysplasias have trouble breathing at night (obstructive sleep apnea or central sleep apnea), so we may ask them to have a sleep study.
  • Sometimes, pregnant women have an ultrasound that raises concerns about the growth of the baby in their womb. In these cases, we take specific ultrasound images that can help identify skeletal dysplasias before birth.

  • Our staff includes experts who can help explain genetic conditions and the possibility of having a child with a skeletal dysplasia.

Treatment of dwarfism and skeletal dysplasias

Our goal is to help children, adolescents and adults with skeletal dysplasias function well and have a high quality of life. This means we are ready to treat all aspects of the disorder, from limb and spine problems to social and family issues, through our Skeletal Health Program.

Medical centers that do not specialize in skeletal dysplasias rarely see these conditions. At Seattle Children’s, we see many children with skeletal dysplasias. Our orthopedic staff is highly skilled and very experienced in treating these conditions.

We manage all aspects of care, including corrective orthopedic (bone) surgery, medicines to strengthen bones and supportive and medical care to treat other issues.

  • In children with skeletal dysplasias, sometimes the arms and legs grow crooked. This can cause hip or knee pain and make walking and running difficult. In some cases, surgery to realign the joints may be helpful.

    The options include:

    • Putting metal plates and screws into the growth plate (tethering the growth plate) in one or more of your child’s bones to correct the way a limb is growing
    • Cutting a bone, straightening it and then fixing it in place using metal plates and screws
  • Sometimes arms and legs are so short that it is difficult for a child to manage daily activities like cleaning themselves. In these cases, you and your child’s doctor may consider limb lengthening.

    In this surgery, the doctor cuts the child’s bone and attaches one of these devices to the bone on both sides of the cut:

    • A frame called a distractor, which is outside the body and goes through the skin into the bone
    • A rod that is placed into the bone and can be adjusted with magnets

    Over time, doctors adjust the device to gradually pull the pieces of bone away from each other. New bone forms in between, making the healed bone longer.

  • In children with dwarfism, common problems include a sideways curve in the spine (scoliosis) and a forward curve in the middle of the spine (kyphosis) that is larger than normal. If your child has severe scoliosis or kyphosis, you and your child’s doctor may consider surgery that uses metal rods and screws to help straighten the spine. Some children need growing rods.

    Experts in our Spine Program treat spine problems linked with dwarfism and skeletal dysplasias.

  • Spinal stenosis is another condition that often affects people with dwarfism. The canal that the spinal cord runs through is narrower than usual, which can put pressure on the spinal cord. This causes pain and weakness in your child’s arms and legs. It may also cause breathing trouble.

    In these cases, you and your child’s doctor may consider surgery to open up the spinal canal to take pressure off the spinal cord and nerves.

  • Medicines like these may help protect your child’s skeleton:

    • Pamidronate. This belongs to a group of medicines called bisphosphonates. These medicines allow bone mass to increase by slowing normal bone breakdown. Pamidronate is used in children with low bone mineral density and fractures, including children with osteogenesis imperfecta. Read more about pamidronate (PDF).
    • Enzyme replacement therapy. Some types of skeletal dysplasia occur when the body is missing an enzyme or the enzyme does not work the way it should. Medicine to provide enough working enzyme may reduce the effects of the disease.
    • Vitamin D. Supplements of vitamin D may be important to building strong bones, especially if your child’s body has trouble absorbing or using enough vitamin D from their diet alone.
  • Your child’s team in the Skeletal Health Program will involve as many specialists your child needs, based on how your child is affected. We often work closely with experts from Audiology and Dentistry, for example, because skeletal dysplasia can affect the skull, ears, jaw and teeth as well as the limbs and spine.

  • We understand the social and physical challenges your child and family may face. We offer social, medical and psychological support services, both at Seattle Children’s and in your child’s community. We encourage families to connect with organizations like Little People of America, Inc., the Osteogenesis Imperfecta Foundation, the National MPS Society and Camp Korey.