Saturday, July 10, 2010

Clubfoot update - Chromosome 17 anomaly in inherited clubfoot cases

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Clubfoot update - genetic link

Small recurrent DNA duplications, as well as deletions, on chromosome 17 are currently the most commonly known cause of inherited clubfoot deformity,

Microarray test results

Chromosomal microarray test that is commonly used for evaluating children with developmental disorders, such as autism. Since few genes have previously been implicated in clubfoot, this discovery represents the most common cause of isolated clubfoot to date. This technology can be used immediately for genetic testing. The DNA duplications on chromosome 17 were found during preliminary screenings performed in 40 patients with inherited clubfoot, which the researchers determined were in the same region previously linked with limb abnormalities, developmental delays and heart defects. However, such duplications were not found among 700 control subjects without clubfoot. 

Family trait

To confirm these chromosomal duplications were inherited, Gurnett’s team ran the same tests on 10 family members of the three patients with duplications. Hip abnormalities, including hip dysplasia, were also seen in some of the patients. These genetic findings may allow orthopedic surgeons to better predict response to clubfoot treatment and also to identify a clubfoot patient group that may need careful hip screening as well.they were present in 6% of familial clubfoot cases tested and were associated with clubfeet that were rigid and prone to a difficult treatment course

Finding the causes of congenital clubfoot — the most common musculoskeletal birth defect — is of critical importance to provide counseling to the families, help in the understanding of the natural history of the deformity after correction and, eventually, in the development of treatments based on the basic molecular abnormality. This study demonstrates that in a small subset of patients (4 out of 66) with congenital clubfoot, a chromosomal abnormality is associated with the deformity. Interestingly, this genetic variation is also associated with other abnormalities including short stature, hip dysplasia, and subtle nail and bony deformities. This later finding separates these patients from the most common form of clubfoot, idiopathic clubfoot, and highlights the importance of careful clinical evaluation when ascertaining patients for genetic studies. In summary, this is an important study that adds to our current understanding of this common birth defect.
– Jose A. Morcuende, MD, PhD
The Ponseti Clubfoot Treatment Center
University of Iowa
Iowa City, Iowa