What Is Kniest Dysplasia?

Kniest dysplasia is a type of skeletal dysplasia. Skeletal dysplasias are conditions that cause problems with how cartilage and bone grow. Kniest dysplasia (k’neest dis-PLAY-zhuh) also can lead to problems with hearing and seeing.

What Are the Signs & Symptoms of Kniest Dysplasia?

Signs and symptoms of Kniest dysplasia include:

• dwarfism (height less than 4 feet, 10 inches [145 cm] as an adult)
• short arms and legs
• wide forehead and wide-set eyes
• a round face with a flattened nose and small chin
• cleft palate
• stiff, swollen joints that can’t bend or straighten fully (called contractures)
• flat feet
• knock-knees (knees curve in)
• curved spine
• instability of the neck bones
• vision problems
• hearing loss
• pectus carinatum
• hip problems

Most children with Kniest dysplasia don’t have every sign and symptom listed here. There is a lot of variability. Kniest dysplasia does not affect intelligence.

What Causes Kniest Dysplasia?

Kniest dysplasia happens because of a gene change (mutation). The changed gene causes a problem with the growth plate of the bone, which leads to abnormal bone growth and shape. The changed gene also works in the eyeball, which can lead to vision problems.

Another skeletal dysplasia — spondyloepiphyseal dysplasia congenita (SEDc) — happens when there is a different change in the same gene. Because this changed gene affects both conditions, children with Kniest dysplasia and SEDc can have similar signs and symptoms.

Kniest dysplasia can happen when a child inherits a changed gene from a parent or, more often, from a new changed gene (a new mutation and neither parent has Kniest dysplasia).

A genetic counselor can help families understand how the condition can run in families.

How Is Kniest Dysplasia Diagnosed?

Sometimes Kniest dysplasia is found before birth if a prenatal ultrasound shows short arms and legs. Genetic testing (through amniocentesis) can confirm the diagnosis. If there’s a family history of Kniest dysplasia, and the family’s gene change is known, an amniocentesis or chorionic villus sampling (CVS) can check the fetus for it too.

Kniest dysplasia may also be diagnosed at birth. The diagnosis is made by looking at the child’s growth, physical features, X-rays, and testing for the gene change.

How Is Kniest Dysplasia Treated?

A team of health care specialists care for people with Kniest dysplasia. The specialists can include:

• an orthopedic surgeon: for bone and joint problems
• a neurologist/neurosurgeon: for spinal cord problems
• a genetics doctor: to help families understand the genetic changes and to plan for future medical care
• an ophthalmologist: for eye problems
• an otolaryngologist (ear, nose, and throat [ENT] doctor): for help with hearing problems
• a pulmonologist: for breathing problems
• a pediatrician: for routine care
• a physical therapist: for help with muscle strength and joint motion
• an occupational therapist: for help with writing, eating, and other everyday activities

How Can Parents Help?

Your child needs the support of family and friends. To help your child:

• Treat your child according to their age, not their size, and encourage others to do the same.
• Talk about Kniest dysplasia as a difference rather than a problem. Your attitude can help your child develop good self-esteem.
• Find ways to adapt. For example, get a light switch extender and a stepstool so your child can turn the lights on and off. Encourage your child’s school to make similar changes that can help.
• If someone asks a question about your child’s Kniest dysplasia, answer as simply as possible. For example, if someone asks why your child is short, say, “William is shorter because his bones grow differently than yours.” Then, mention something special about your child. For example, “William has so many different interests. You should see his baseball card collection.” This shows your child that things other than Kniest dysplasia make them special.
• Teach your child that being teased or bullied is not OK. If your child is teased or bullied at school, work with your child, teachers, and administrators to end it.
• Encourage your child to find a hobby or activity to enjoy. Help your child try many different activities, like sports, music, art, computers, writing, and photography. Be sure to check with your doctor about any sports your child should avoid.

What Else Should I Know?

To help your child stay well and manage any problems, it’s important for your child to have regular medical care. Be sure to go to all doctor visits, and follow all recommendations. Talk to anyone on the care team or a hospital social worker about resources that can help you and your child.

Health problems can come up that need to be treated right away. So regular medical follow-up should include exams by an:

• ophthalmologist to check for nearsightedness and to check the retina
• orthopedic doctor to watch for neck instability and other issues that can come up with the back and legs

Support groups can be helpful for kids and their families. Ask the care team for recommendations. You also can find support and more information online at:

• Little People of America
• NORD