Reason and forms
The thirteenth chromosome in this syndrome is present in three copies instead of two. Most often, the cause is non-disjunction of chromosomes during egg maturation, and the likelihood of such an error increases with the age of the mother. In the mosaic form, only a portion of the cells have an extra chromosome, so the symptoms are milder and the life expectancy is longer. A translocation variant occurs when a fragment of the thirteenth chromosome joins another; in this case, one of the parents may be a carrier of a balanced rearrangement without any signs of the disease, and then the risk of recurrence in the family is noticeably higher.
- Complete trisomy 13 is the most common variant
- Mosaic shape with softer manifestations
- Translocation form with inherited risk
- Random error in germ cell division
- Risk increases with maternal age
- Not related to diet, medications or lifestyle
Manifestations
The main blow falls on the brain and face, which are formed from common rudiments. Holoprosencephaly—underdevelopment of the separation of the hemispheres—as well as microcephaly are common. On the side of the face, typical features include cleft lip and palate, microphthalmos or absence of eyeballs, and deformed, low-set ears. There are additional fingers on the hands and feet. The skin of the scalp may have areas without covers. There is almost always a congenital heart defect, and often kidney anomalies. Children do not suck well, they have convulsions and stop breathing.
- Microcephaly and brain defects
- Cleft lip and palate
- Microphthalmos and other eye abnormalities
- Deformed, low-set ears
- Extra fingers and toes
- Skin defects of the scalp
- Heart and kidney defects
- Seizures, apnea, feeding difficulties
Detection during pregnancy
Unlike some other chromosomal syndromes, trisomy 13 is usually accompanied by gross defects that are clearly visible on ultrasound. Already in the first trimester, increased thickness of the nuchal translucency and abnormalities in brain development may become noticeable. In the second trimester, facial clefts, heart defects, extra fingers, and fetal growth retardation are visible. Biochemical screening is less indicative than ultrasound. A non-invasive prenatal test using the mother's blood helps clarify the probability, but confirmation requires examination of fetal cells.
- Ultrasound of the first trimester with assessment of the nuchal translucency
- Detailed ultrasound of the fetus in the second trimester
- Fetal echocardiography
- Non-invasive prenatal DNA test
- Chorionic villus sampling or amniocentesis
- Karyotyping of fetal cells
Confirmation and genetic consultation
The diagnosis is reliable only after chromosome analysis. It determines the form of the syndrome, which determines both the prognosis and the risk of recurrence in the family. If a translocation is detected, both parents are offered karyotyping: carriage of a balanced rearrangement does not in any way affect the health of the person himself, but significantly increases the likelihood of recurrence in the offspring. The geneticist explains the results in simple language, assesses the risk for future pregnancies and talks about planning options, including early prenatal diagnosis.
- Karyotyping of a child or fetal cells
- Molecular methods for fast results
- Karyotyping of both parents during translocation
- Assessing individual risk of recurrence
- Planning prenatal diagnostics in advance
- Psychological support for family
Helping a child
There is no treatment that eliminates the extra chromosome, so help is aimed at the comfort of the child and support of the family. The most important task is to provide feeding and pain relief, support breathing if necessary, and control seizures. The issue of surgical interventions, including correction of cleft and heart defects, is decided by the council individually, taking into account the severity of the condition and the opinion of the parents. The palliative service helps organize care at home. It is important for parents to know that what happened was not a consequence of their actions, and to receive clear information about the prognosis.
- Palliative approach and pain management
- Tube feeding with weak sucking
- Seizure control and respiratory support
- Individual decision about surgical correction
- Home care organization
- Parental support and genetic counseling
