Kniest Dysplasia

Frequently asked questions about Kniest Dysplasia

DESCRIPTION Kniest dysplasia is a very rare condition that leads to short stature, malformed bones and joints, and sometimes vision and hearing problems. The condition was named after Dr. Wilhelm Kniest in 1952.

 
FREQUENCY: One in 1,000,000 live births. The disorder affects males and females in equal numbers.

 
SYMPTOMS:
At birth:

 

  • Short limbs, barrel-chest, eye problems, joints that do not extend all the way and may be swollen, decreased hearing, cleft palate, and a round mid-face with flat and round facial features.
  • Other symptoms include a curved spine, instability of the cervical spine at C1 and C2 (vertebras in the neck), short neck, clubfoot, cleft palate, and poorly formed femur heads.
  • Inguinal hernias may also be present.
  • A distinctive feature is a ‘Swiss cheese’ pattern in cartilage observed in X-rays.

In children and adults:

  • Spinal curvature may worsen over time.
  • Joint contractures (inability to straighten) may get progressively worse, joints may get more swollen.
  • Hearing and vision problems can also progress over time.

Note: A person may have some, but not necessarily all of the above symptoms.

Intelligence is usually unaffected.
GENETICS: Kniest is a random genetic change. Kniest is usually sporadic and is due to the chance occurrence of a genetic mutation. It is the result of a genetic defect in encoding type II collagen (COL2A1). Most Kniest mutations are due to small changes on chromosome 12. Note that this is a purely random occurrence and that there is nothing either parent did to cause this genetic change.

 

Kniest has an autosomal dominant inheritance. When a person has Kniest, he/she has a 50% chance having a child with Kniest.
IS INTELLIGENCE AFFECTED?
People with Kniest usually have normal intelligence.

 
PRENATAL TESTING:
Sometimes.

 

Since some mutations for Kniest are known it is possible to diagnose it by amniocentesis or CVS. Parents with Kniest who wish to have children and obtain prenatal genetic testing need to first know which Kniest mutation they have. Therefore, it is recommended that people with Kniest see a genetic counselor before becoming pregnant.

Kniest can sometime be diagnosed prenatally by sonogram towards the end of t he second trimester.
EXPECTED HEIGHT:

 

 100-140 CM or 39-55 in.
HEIGHT/WEIGHT CHART:
Kniest is a very rare condition with a lot of variation. There is no height and weight chart at this time. It is important to be as lean as possible to reduce stress on joints.

 
MEDICAL CARE:
Neck and vertebrae An evaluation of the C1 and C2 should be done to detect odontoid hypoplasia; spinal fusion may be indicated. Even though a spinal fusion may not be needed, lax ligaments in the neck could lead to spinal injury during anesthesia, contact sports, and car accidents. There also may be chest constriction, which can cause decreased lung capacity. Therefore, a person should be closely monitored during anesthesia and for complications during a respiratory infection. Please see KSG Athesthesia Page for more information about anesthesia concerns.

 

Regular eye exams should be done by an ophthalmologist to evaluate for near-sightedness and detached retinas. A detached retina is an urgent condition. Any unusual eye symptoms should be reports to an ophthalmologist right away.

Hearing should be checked and ear infections should be closely monitored. Tubes may need to be placed in the ear.

During anesthesia, there are risks related to cervical spine instability, lung capacity, and small airways. Anesthesia should NOT be performed until these have been evaluated. Please see KSG Athesthesia Page for more information about special concerns concerning anesthesia.

Orthopedic care may be needed to evaluate hip, spinal, and knee complications. Hip replacement is sometimes warranted in adults. Additionally, due to poorly developed type II collagen, people with Kniest may experience arthritis.

Always check with your medical doctor to evaluate your particular health care needs.
MEDICAL CAUTIONS: Due to neck instability, persons with Kniest should exercise caution to avoid activities/sports that could result in trauma to the neck or head.

 

Anesthesia: See above.
More information:
   
REFERENCES: To see most current publications, please see Information about SED/SMD section for a list of references by condition. The Do Your Own Research section has instructions on how to do your own internet research. The Explanation of Medical Terms definitions of science terms.
Three young women with Kniest Dysplasia. This photo was taken at a KSG event.

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