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X-linked spondyloepiphyseal dysplasia tarda
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Reviewed June 2008
What is X-linked spondyloepiphyseal dysplasia tarda?
X-linked spondyloepiphyseal dysplasia tarda is a condition that impairs bone growth and occurs almost exclusively in males. The name of the condition indicates that it affects the bones of the spine (spondylo-) and the ends (epiphyses) of long bones in the arms and legs. "Tarda" indicates that signs and symptoms of this condition are not present at birth, but appear later in childhood, typically between ages 6 and 10.
Males with X-linked spondyloepiphyseal dysplasia tarda have skeletal abnormalities and short stature. Affected boys grow steadily until late childhood, when their growth slows. Male adult height ranges from 4 feet 10 inches to 5 feet 6 inches. Individuals with X-linked spondyloepiphyseal dysplasia tarda have a short trunk and neck, and their arms appear disproportionately long. Impaired growth of the spinal bones (vertebrae) causes the short stature seen in this disorder. The spinal abnormalities include flattened vertebrae (platyspondyly) with hump-shaped bulges, progressive thinning of the discs between vertebrae, and an abnormal curvature of the spine (scoliosis or kyphosis). Other skeletal features of X-linked spondyloepiphyseal dysplasia tarda include an abnormality of the hip joint that causes the upper leg bones to turn inward (coxa vara); a broad, barrel-shaped chest; and decreased mobility of the elbow and hip joints. Arthritis often develops in early adulthood, typically affecting the hip joints and spine.
How common is X-linked spondyloepiphyseal dysplasia tarda?
The prevalence of X-linked spondyloepiphyseal dysplasia tarda is estimated to be 1 in 150,000 to 200,000 people worldwide.
What genes are related to X-linked spondyloepiphyseal dysplasia tarda?
Mutations in the TRAPPC2 gene (often called the SEDL gene) cause X-linked spondyloepiphyseal dysplasia tarda. The TRAPPC2 gene provides instructions for producing the protein sedlin. The function of sedlin is unclear. Researchers believe that sedlin is part of a large molecule called the trafficking protein particle (TRAPP) complex, which plays a role in the transport of proteins between various cell compartments (organelles). Because sedlin is active (expressed) in cells throughout the body; it is unclear why mutations in the TRAPPC2 gene affect only bone growth.
Read more about the TRAPPC2 gene.
How do people inherit X-linked spondyloepiphyseal dysplasia tarda?
X-linked spondyloepiphyseal dysplasia tarda is inherited in an X-linked recessive pattern. The TRAPPC2 gene is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation must be present in both copies of the gene to cause the disorder. Males are affected by X-linked recessive disorders much more frequently than females. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
In X-linked recessive inheritance, a female with one mutated copy of the gene in each cell is called a carrier. She can pass on the altered gene, but usually does not experience signs and symptoms of the disorder. In rare cases, however, females who carry a TRAPPC2 mutation may develop arthritis in early adulthood.
Where can I find information about diagnosis or management of X-linked spondyloepiphyseal dysplasia tarda?
These resources address the diagnosis or management of X-linked spondyloepiphyseal dysplasia tarda and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about X-linked spondyloepiphyseal dysplasia tarda?
You may find the following resources about X-linked spondyloepiphyseal dysplasia tarda helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for X-linked spondyloepiphyseal dysplasia tarda?
What if I still have specific questions about X-linked spondyloepiphyseal dysplasia tarda?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding X-linked spondyloepiphyseal dysplasia tarda?
arthritis ; carrier ; cell ; chromosome ; coxa vara ; dysplasia ; expressed ; gene ; inheritance ; inherited ; joint ; molecule ; mutation ; prevalence ; protein ; recessive ; scoliosis ; sex chromosomes ; short stature ; stature ; X-linked recessive
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (4 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.