Frequently asked questions about
Spondyloepiphyseal Dysplasia Congenita (SEDC)

There are many types of SED, the most common is Spondyloepiphyseal Dysplasia Congenita (SEDC). Other types include:
DESCRIPTION: Spondylo- means spinal, epiphyseal – growth plates at the end of long bones, dysplasia – abnormal bone growth or development and congenita – means present at birth.

FREQUENCY: One in 100,000 live births. The disorder affects males and females in equal numbers.

Clinical signs of SEDC are short trunk dwarfism, barrel-chested, myopia (near-sightedness), retinal detachment, knees may be misaligned, decreased hearing, cleft palate, and flat facial features. The spine may be curved, cervical spinal compression, short neck, clubfoot, poorly formed femur heads, and instability of the cervical spine at C1 and C2. Clubfoot and cleft palate will need to be surgically repaired.

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

Intelligence is usually unaffected.

SEDC is a random genetic mutation. SEDC 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). Note that this is a purely random occurrence and that there is nothing either parent did to cause this genetic change. SEDC is an autosomal dominant inheritance.

When a person has SEDC, he/she has a 50% chance of passing the gene onto a child.

People with SEDC usually have normal intelligence.

Although the SEDC gene has been located, there is variability in the location of the gene among persons with SEDC. Prenatal gene testing is available, but it is expensive.


Expected adult height ranges from 36″ – 67″ (90cm – 167.5cm).
There is a height chart that has been developed for SEDC. It is important to be as fit and lean as possible to put less strain on the joints.

It is important to note that this chart was based on only 62 people with SEDC. There is a lot of variation in height among people with SEDC. This chart can serve as a helpful guide. Please click here to open the JPEG file.

A height/weight chart developed for average statured people may not be the appropriate measure for a person with short-stature.

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 for more information about anesthesia concerns.

Regular eye exams should be done by an ophthalmologist to evaluate for near-sightedness and detached retinas.

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

Symptoms such as a clubfoot or cleft palate may need to be corrected.

During anesthesia, there are risks related to cervical spine instability, lung capacity, and small airways. Anesthesia should NOT be performed until these things have been evaluated. Please see 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, the person may experience arthritis.

You should always check with your medical doctor to evaluate your particular health care needs.

MEDICAL CAUTIONS: Due to neck instability, persons with SEDC 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 search PubMed.

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 Glossary section explains medical terms.