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URL of this page: https://medlineplus.gov/genetics/condition/spondyloepiphyseal-dysplasia-congenita/

Spondyloepiphyseal dysplasia congenita

Description

Spondyloepiphyseal dysplasia (SED) congenita is a disorder of bone development that causes short stature with a particularly short torso and short arms and legs. The parts of the body are not proportional to one another (disproportionate short stature) in people with this condition. Affected individuals typically have hands and feet that are of average size. SED congenita affects the bones of the spine (spondylo-) and the ends (epiphyses) of the long bones in the arms and legs. People with this condition also have problems with vision and hearing. The word "congenita" indicates that the condition is often noticeable at birth. The signs and symptoms of SED congenita can vary among affected individuals.

People with SED congenita have an adult height that ranges from 3 feet to almost 5 feet. Affected individuals may develop abnormal curvature of the spine (scoliosis or kyphosis), which can worsen during childhood. Instability of the spinal bones (vertebrae) in the neck can cause these bones to shift, which increases the risk of damage to the spinal cord. 

Other skeletal issues in individuals with SED congenita can include flattened vertebrae (platyspondyly), an abnormality of the hip joint that causes the upper leg bones to turn inward (coxa vara), and inward- and upward-turning feet (clubfoot). Arthritis and decreased joint mobility often develop early in life. An abnormally short, broad, and barrel-shaped chest can cause problems with breathing. People with SED congenita may also have breathing problems due to weakness of the windpipe. 

SED congenita often causes mild differences in facial features such as underdeveloped cheek bones (malar hypoplasia). Some affected individuals have a particular group of physical features called Pierre Robin sequence, which includes an opening in the roof of the mouth (cleft palate), a tongue that is placed further back than normal (glossoptosis), and a small lower jaw (micrognathia). Severe nearsightedness (high myopia) is common in SED congenita, as are other eye problems that can impair vision such as a tearing of the light-sensitive tissue at the back of the eye (retinal detachment). Some people with SED congenita have hearing loss.

Some disorders, such as spondyloepiphyseal dysplasia with premature-onset arthrosis and Namaqualand type hip dysplasia, are similar to SED congenita but have milder signs and symptoms. These milder conditions were once thought to be separate disorders, but they are now considered to be part of SED congenita. People with these disorders typically have joint pain and stiffness, which can restrict movement. Symptoms can begin in childhood and often worsen over time.

Frequency

Though it is one of the more common skeletal dysplasias, SED congenita is rare. The exact prevalence is unknown. 

Causes

SED congenita is caused by variants (also called mutations) in the COL2A1 gene. This gene provides instructions for making a protein that forms type II collagen. This type of collagen is found in the clear gel that fills the eyeball (the vitreous) and in cartilage. Cartilage is a tough, flexible tissue that makes up much of the skeleton during early development; most cartilage is later converted to bone. Type II collagen is essential for the normal growth and development of bones and other connective tissues.

The variants in the COL2A1 gene that cause SED congenita interfere with the assembly of type II collagen molecules, which prevents bones and other connective tissues from developing properly. This impaired bone development leads to short stature and the other characteristic features of SED congenita.

Inheritance

Typically, SED congenita is inherited in an autosomal dominant pattern, which means one copy of the altered COL2A1 gene in each cell is sufficient to cause the disorder. Many cases of this condition are the result of a new (de novo) variant in the COL2A1 gene that occurs during the formation of reproductive cells (eggs or sperm) in an affected individual's parent or during early embryonic development. These affected individuals have no history of the disorder in their family.

In rare cases, SED congenita is inherited in an autosomal recessive pattern, which means both copies of the COL2A1 gene in each cell must have a variant to cause the disorder. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

Other Names for This Condition

  • SED congenita
  • SED, congenital type
  • SEDc
  • SEDC
  • Spondyloepiphyseal dysplasia congenita (SEDC), COL2A1-related
  • Spondyloepiphyseal dysplasia, congenital type

Additional Information & Resources

Genetic Testing Information

Genetic and Rare Diseases Information Center

Patient Support and Advocacy Resources

Clinical Trials

Catalog of Genes and Diseases from OMIM

Scientific Articles on PubMed

References

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