A diagnosis of TCS is made based upon a thorough clinical evaluation, a detailed patient history and identification of characteristic physical findings. Many associated abnormalities such as malformation or absence of the external ear are present at birth (congenital).
Clinical Testing and Work-Up
Specialized x-ray studies will confirm the presence and/or extent of certain observed craniofacial abnormalities. For example, such imaging tests show the abnormal smallness of the jaw (micrognathia) due to underdevelopment of the lower jaw bone (mandibular hypoplasia), the presence and/or extent of hypoplasia affecting certain parts of the skull, and/or the presence of additional malformations of the ear that cannot be seen during clinical evaluation.
TCS can be detected before birth (prenatally) by amniocentesis and chorionic villus sampling if a TCOF1, POLR1C, or POLR1D mutation has been identified in an affected family member. In certain cases, fetal ultrasonography, which uses reflected sound waves to create an image of the developing fetus, can reveal characteristic findings suggestive of TCS.
In addition, in those affected individuals who exhibit few signs, a thorough clinical examination and x-ray imaging tests of the craniofacial area can demonstrate the subtle expression of certain characteristic features (e.g., hypoplasia of zygomatic arches) associated with TCS. Because TCS shares several physical features that may occur in other craniofacial syndromes, many researchers suggest that stronger diagnostic confirmation be made through molecular genetic testing and/or, in some cases, a careful, detailed family history.
Molecular genetic testing to confirm a diagnosis is available through commercial and academic research laboratories to detect mutations in the TCOF1, POLR1C and POLR1D genes. Approximately 90-95% of individuals have an identifiable mutation of the TCOF1 gene.
Relatives, especially parents and siblings, of an individual diagnosed with TCS should be carefully examined because mild cases often go unrecognized and undiagnosed.