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Trismus-Pseudocamptodactyly Syndrome

Background
Who should be tested?
Testing Methodology
Potential Outcomes Interpretation of Test Results
Caution
For More Information

Background

Patients with trismus-pseudocamptodactyly syndrome may show cardiac myxomas, spotty skin pigmentation alone or in combination with cutaneous lesions. Most affected individuals have distal arthrogryposis, including pseudocamptodactyly of the hands and feet, trismus, or both, which improves symptomatically with aging.

Trismus-pseudocamptodactyly syndrome is an autosomal dominant disorder caused by a deficiency of a perinatal skeletal myosin heavy chain. The syndrome is caused by mutations in the MYH8 gene which has been mapped to chromosome 17p13.1. A single mutation, p.Arg674Gln, has been described in several families of Belgian descent.

Trismus-pseudocamptodactyly syndrome is present when an individual has one copy of the defective gene. There is a 50% chance that baby will inherit the mutation for trismus-pseudocamptodactyly syndrome and thus may develop symptoms in the perinatal period. There is a 50% chance that the baby will not have trismus-pseudocamptodactyly syndrome.

Who should be tested

• individuals clinically suspected of being affected with trismus-pseudocamptodactyly syndrome
• pregnancies at increased risk of being affected with trismus-pseudocamptodactyly syndrome

Testing Methodology

Direct Mutation Analysis: All samples are analyzed by direct sequence analysis of the 38 exons of the MYH8 gene.

Potential Outcomes & Interpretation of Test Results

Cautions:

• Current molecular testing will not detect all possible mutations in this gene. A negative result does not rule out the possibility that the individual carries a rare MYH8 mutation not detected by this assay.
• Test results should be interpreted in the context of clinical findings, family history, ethnic background and other laboratory data.
• This test was developed and its performance characteristics validated by the Molecular Genetics Laboratory at the Hospital for Sick Children. It has not been cleared or approved by the U.S. Food and Drug Administration. The FDA has determined that such clearance or approval is not necessary. This test is used for clinical purposes.

For More Information:

• Online Mendelian Inheritance in Man - Item #158300
• Veugelers M. et al. (2004) Mutation of perinatal myosin heavy chain associated with Carney complex variant. New Eng J Med 351:460-9.
• To locate a genetics center near you, please visit Canadian Association of Genetic Counsellors website.