Saethre

SAETHRE-CHOTZEN SYNDROME:

The classical phenotype described for Saethre-Chotzen syndrome is synostosis of the coronal sutures of the skull resulting in facial dysmorphologies including asymmetry to the face, hypertelorism and maxillary hypoplasia. Frequently, a high forehead with a low hairline, drooping eyelids, conductive deafness, cleft palate, deviated nasal septum and malocclusions are also present. Brachydactyly and cutaneous syndactyly between the second and third fingers and toes are also seen in the majority of cases. Mild to moderate mental retardation is often present. The symptoms overlap with other craniosynostosis syndromes, including Crouzon, Apert, Pfeiffer and Jackson-Weiss syndromes, which are related to the FGFR gene family.

The incidence of Saethre-Chotzen syndrome has been estimated at 1 in 25-50,000 live births; however, this number is probably underestimated. Saethre-Chotzen syndrome may be caused by as a variety of mutations on the TWIST gene (chromosome 7p21). About one-half of the mutations are insertions or deletions, and many of the remainder are missense or nonsense point mutations. Finally, between 10%-20% of cases are due to deletions of the entire gene. In order to expedite diagnosis, reduce the total cost of testing, and improve the ease of ordering this testing may be combined with testing for the various FGFR syndromes in the Craniodysmorphology Panel.

REASONS FOR REFERRAL:

To confirm the nature of the dwarfism in an affected individual.
To determine whether Saethre-Chotzen syndrome is responsible for abnormalities in the skull, eyes, or limbs.
To discriminate between syndromes with different but overlapping clinical symptoms in an affected individual.
To establish whether the symptoms are spontaneous or inherited within a family.
To evaluate the risk of having a child with Saethre-Chotzen Syndrome.
Individuals at risk who wish prenatal diagnosis.
For ambiguous patients, this test is often included with testing for the FGFR syndromes.

TESTING METHODOLOGY:

PCR amplification and DNA sequencing of the TWIST gene.

SPECIMEN REQUIREMENTS:

Blood EDTA (purple top) tubes:

Newborn: minimum 1-2 mL

Child/Adult: prefer 2 tubes of 3-5 mL

Prenatal testing: Please contact the laboratory for instructions.

A Molecular Genetics Laboratory Test Requisition must accompany the specimen. Contact the Molecular Laboratory at 918-502-1721 to obtain further information.

TURNAROUND TIME: 15 working days

CPT CODES: