WHAT DOES TRISOMY TEST + EXAMINE?
Differences TRISOMY tests
Down syndrome (trizómia 21)
Edwards syndrome (trizómia 18)
Patau syndrome (trizómia 13)
Foetal sex determination
Sex chromosome abnormalities
Klinefelter syndrome (XXY)
XYY syndrome (XYY)
XXX syndrome (XXX)
DiGeorge syndrome (22q11)
Prader-Willi syndrome and Angelman syndrome (15q11)
Cri-du-chat syndrome (5p15)
1p36 deletion syndrome
Wolf-Hirschhorn syndrome (4p16.3)
* If a blood sample cannot be processed by the laboratory in accordance with the principles of good laboratory practice (e.g. in the event of a low foetal DNA concentration in the sample), or if the analytical results do not provide an answer to the diagnostic question, the laboratory offers a repeat examination based on the same blood sample free of charge. Under the circumstances, the period for the delivery of test results will change from 5 to 8 days (this generally applies to about 10% of all samples).
Due to biological and technological limitations, the accuracy of our microdeletion syndrome examination is relatively lower compared to trisomy 21, 18, and 13. Given the generally low occurrence of microdeletions in the population, there have been no studies that would reliably validate the accuracy of our test targeting these syndromes.
|Syndrome name||Localisation||Incidence||Deletion extent|
|DiGeorge syndrome||22q11||1 : 4000||3 – 5 Mb|
|1p36 deletion syndrome||1p36||1 : 5000 – 10 000||1 – 10 Mb|
|Prader-Willi syndrome and Angelman syndrome||15q11||1 : 10 000 – 30 000||2 – 9 Mb|
|Cri-du-chat syndrome||5p15||1 : 20 000 – 50 000||5 – 35 Mb|
|Wolf-Hirschhorn syndrome||4p16||1 : 50 000||2,5 – 30 Mb|
22q11 DIGEORGE SYNDROME
The most frequent microdeletion syndrome, DiGeorge syndrome causes a severe disorder that can manifest in any system or any part of the human body. The symptoms can be treated only in some cases. The disorder is characterised by congenital heart defects (CHDs), immune system disorders, kidney defects, and cleft palate issues, frequently combined with severe mental retardation. The symptoms vary considerably. In some cases (especially those involving less pronounced symptoms), familial transmission and intrafamilial variability can be assumed.
Since CHDs may actually be the only symptom of 22q11 deletion, the syndrome is frequently indicated by prenatal genetic examinations when a congenital hear disorder is detected or when such a disorder is indicated by ultrasound screening.
1p36 DELETION SYNDROME
Similarly to DiGoerge syndrome, 1p36 deletion syndrome is one of the most frequent microdeletion syndromes. It leads to an extremely severe and untreatable disorder characterised by very heterogeneous symptoms. Its main characteristics include mental retardation combined with behavioural disturbances, growth delays, and hypotonia.
15q11 PRADER-WILLI SYNDROME & ANGELMAN SYNDROME
Although they are different from one another in terms of their clinical symptoms, both syndromes are caused by an absence or dysfunction of gene functions in one and the same critical region of chromosome 15. Although most cases are caused by a deletion affecting a critical region of chromosome 15, other cases can be caused by sporadic mutation, methylation disorders, or uniparental disomy rather than deletion. Under the circumstances, it cannot be expected that microdeletion screening will detect all actual Prader-Willi and Angelman syndrome cases.
Prader-Willi syndrome is characterised by hypotonia, poor sucking reflexes, feeding difficulties in early infancy, followed by hyperphagia and obesity from age 2 onwards. Mental retardation is relatively mild, but various other behavioural disorders are present in addition to excessive eating.
Angelman syndrome characteristics are less expressed. Usually not obvious at birth, the clinical symptoms start developing around the age of 12 months. They include psychomotor activity and speech development delays. The patient’s medium mental retardation is accompanied by progressively pronounced behavioural disturbances.
5p15 CRI-DU-CHAT SYNDROME
Cri-du-chat syndrome is an older, cytogenetically defined syndrome (also known as Lejeune syndrome or 5p- syndrome) because more extensive deletions could already be detected using optical microscopes in the era of traditional cytogenetics.
The name “cri-du-chat” (cat’s cry) comes from the leading clinical symptom this syndrome is characterised by in the period of early infancy. Combined with characteristic facial dysmorphia, the symptom is a distinguishing feature of this syndrome in comparison to other disorders involving growth delays, psychomotor retardation, microcephaly, and hypotonia. The scope of actual deletion correlates with the severity of the patient’s disability.
4p16 WOLF-HIRSCHHORN SYNDROME
Wolf-Hirschhorn syndrome (also known as 4p- syndrome) belongs to the same group of syndromes identified by traditional cytogenetics. The severity of its clinical symptoms correlates with the actual scope of deletion. Similarly to cri-du-chat syndrome, this syndrome comes with characteristic facial dysmorphia combined with microcephaly, hypertelorism, protruding eyes, and a short philtrum. Severe growth and psychomotor retardation is accompanied by other serious symptoms, such as hypotonia, epileptic fits, and congenital development defects affecting internal organs (esp. heart and kidney defects).