Spondyloepiphyseal dysplasia, congenita (SEDc) is a skeletal dysplasia that is diagnosable at birth and most significantly affects the skeletal development of the spine and long bones. Individuals with SEDc are short statured with adult height ranging from 85-1 45 cm (33.5-57 inches). In this condition, the extremities are shortened when compared with the average, but appear long in relation to the trunk. The person's hands may be average sized. SEDc is caused by a mutation in collagen. Collagen is an essential connective tissue for bones and is also important in the eyes and other parts of the body. In addition to small stature at birth, individuals with SEDc may have clubfeet, cleft palate, a flat face with wide-set eyes (hypertelorism), a short neck and a barrel-shaped chest. Children develop lumbar lordosis and are often delayed in their motor development. One of the most significant problems that face individuals with SEDc is instability of the cervical spine due to under-development of the odontoid of the second cervical vertebrae, lax (loose) ligaments, and low muscle tone. This instability poses a risk for dislocation between the first and second vertebrae (atlantoaxial) of the cervical spine (neck) and can lead to compression of the spinal cord at that level. SEDc often also includes myopia, mild respiratory problems, and thoracic (mid-spine) kyphosis. Retinal detachment occurs less frequently. Intelligence is normal.
SEDc is caused by mutations in the COL2A1 (type II collagen) gene. Most often an individual with SEDc is born to average-stature parents as the result of a sporadic (de novo) mutation. This mutation is autosomal dominant, so individuals with SEDc have a 50% chance with each pregnancy of having a child with this condition. It is important to note that there is a family of skeletal dysplasias that are caused by different mutations in the COL2A1 that have a spectrum of severity that ranges from lethal to average-statured with minor eye and skeletal findings. There is another form of SED that presents later in life called “SED tarda.” This form of SED is caused by genetic mutations on the X chromosome, not in the COL2A1 gene.
Standard of care for diagnosis of SEDc is based on clinical and radiologic features. Radiologic findings include: delayed ossification of femoral heads, pubic bones and calcaneus (heel), coxa vara (hip deformity), and platyspondyly (flat vertebrae). DNA mutation studies can be done to confirm diagnosis or to identify a parent's mutation in a fetus at risk for being affected.
Prenatal diagnosis is available by CVS (chorionic villus sampling) or amniocentesis when there is a known mutation in an affected parent. A fetus may also be identified with features of SEDc by ultrasound, especially if a parent is affected or has had previously affected child. Features may not be apparent until later in pregnancy.
There is no cure or treatment to prevent the characteristics/symptoms of SEDc. Individuals with SEDc are treated for specific medical complications as they arise. Regular ophthalmologic visits are recommended to follow myopia and assess for potential retinal detachment. X-rays of the cervical spine are recommended annually to assess C-spine stability. If instability is noted, CT scan or MRI may be used to further evaluate for cervical spine compression. If the MRI or CT scan show compression or significant instability, surgical fusion of the spine is usually recommended in order to prevent paraplegia or death. Due to these risks, it is strongly recommended that individuals with SEDc avoid certain activities that may put their cervical spine at risk. These activities include: American football, wrestling, diving, gymnastics/tumbling, full contact ice hockey, rugby, trampoline, hanging upside down by knees and heading in soccer. If the person with SEDc should need general anesthesia, it is important that the cervical spine be assessed beforehand and precautions taken. For instance, the neck should not be fully extended back for intubation. Due to the small chest size, individuals with SEDc are at risk for restrictive airway disease (RAD) and should be monitored with pulmonary function tests.
Some of the most difficult aspects of having SEDc are not the medical issues, but rather the environmental and social issues that arise for a person of short stature and/or with an orthopedic disability. It is important to work with the family on their adjustment to the diagnosis and what that will mean for the child and their family. Individuals with SEDc and their families should receive assistance in developing strategies for functioning in a world made for taller people. Participation in household, school, and social activities are examples of activities that may all be significantly impacted by the condition. Stools, extenders for reaching, and extra time to get to class, are all examples of modifications that may be required. In addition to the functional aspects, being short-statured and orthopedically handicapped carries great stigma. It is important to help the people with SEDc and their families to mentally prepared themselves for the teasing, staring, and ignorance they may face and learn coping mechanisms and reactions to these behaviors. Little People of America (LPA) is the support organization for all people of short stature and their families. This organization can be extremely helpful in assisting with social adjustment and, more than anything else, letting people with short stature know that they are not alone in their circumstances.
Genetics Home Reference: Spondyloepiphyseal dysplasia congenita General information about SEDc provided by the National Library of Medicine. Also includes links to many related sites.
Created by: Ericka Okenfuss, MS, Deirdre Popplewell, RN
Reviewed by: Kimberly Barr, MS CGC
Last reviewed: Monday, July 13, 2009
Last Updated: Friday, March 9th, 2007 5:07 PM