7019. Karyotyping (blood, Williams syndrome, GTG- and FISH-methods)

Karyotyping (GTG and FISH methods) allows for highly accurate detection of deletions on chromosome 7, the cause of Williams syndrome. This test is recommended for developmental delays, specific facial features, and suspected microdeletion syndrome.

Williams syndrome is a rare genetic disorder caused by a microdeletion of the 7q11.23 region on the long arm of chromosome 7. Approximately 26-28 genes are lost, including the key gene, ELN, which is responsible for the synthesis of the protein elastin, which is important for the elasticity of vascular walls and connective tissue.

A defect in this chromosomal region results in a characteristic combination of symptoms:

• specific facial features (the so-called elfin appearance);
• impaired cognitive development, especially spatial reasoning;
• elevated calcium levels (hypercalcemia) in infancy;
• heart and vascular defects (often supravalvular aortic stenosis);
• highly sociable, outgoing, and prone to anxiety.

Delayed speech and motor development. For diagnosis, GTG staining (classical karyotyping) and FISH analysis (fluorescence in situ hybridization) are used, which allows for the detection of microdeletions with high accuracy, even when traditional karyotyping does not provide sufficient resolution.

For children:

• with delayed speech, psychomotor, or physical development;
• with characteristic appearance and behavioral characteristics;
• with heart or vascular defects;
• if microdeletion syndrome is suspected (especially in cases of a negative standard karyotype).

For parents (when planning a subsequent pregnancy):

• if there is already a child with confirmed Williams syndrome in the family;
• for assessing hereditary risks and prenatal diagnosis in subsequent pregnancies.

• Venous blood

In order to exclude factors that may affect the test results, we recommend to follow the preparation rules: