Trisomy 14
| Classification according to ICD-10 | |
|---|---|
| Q92.0 | Complete trisomy, meiotic nondisjunction |
| Q92.1 | Complete trisomy, mosaic (mitotic nondisjunction) |
| Q92.2 | Partial trisomy, major form
A whole arm or more doubled |
| Q92.3 | Partial trisomy, minor form
Less than a whole arm doubled |
| Q92.4 | Chromosome duplications that are only visible in the prometa phase |
| Q92.5 | Chromosome duplications, with other complex rearrangements |
| ICD-10 online (WHO version 2019) | |
The trisomy 14 is a through the triple ( trisomic ) presence of genetic material from chromosome 14 caused disability based on a genome mutation .
frequency
Girls are more likely to be born with trisomy 14 than boys. Live births are rare, however, as most children die in the course of pregnancy , which means that miscarriages often occur in the early stages . An examination of 776 miscarried fetuses revealed a trisomy 14 in 15 of them. Since the first description, over 20 case studies of living children with trisomy 14 have been documented.
to form
- Partial trisomy 14 : Most living children with trisomy 14 have this type in which a chromosome segment from one of the two chromosomes 14 is tripled. The chromosomes are indeed, as usual, in duplicate in all body cells, but one is part ( Part ) verzweifacht one of the two chromosomes 14, whereby one of the chromosomes is slightly longer than the other. The genetic information in this section is therefore available in three ways.
- Mosaic trisomy 14 : Second most common type of trisomy 14 in living children. The whole chromosome 14 or part of it is not present in triplicate in all body cells, but at the same time there is a cell line with the usual diploid set of chromosomes. The presence of several karyotypes within an organism is called a mosaic in genetics .
- Free trisomy 14 : Type in which chromosome 14 is completely triple in all body cells.
- Translocation trisomy 14 : Type in which chromosome 14 is present in triplicate in all body cells. However, one of the three chromosomes 14 or part of it has attached itself to a different chromosome. This "change of location" of a chromosome or a piece of chromosome is known as a translocation in genetics .
Symptoms
The characteristics of children with trisomy 14 are variable, which may result in a. seems to depend on the percentage of trisomal cells (in mosaic trisomy) and / or the trisomal chromosome segment (in partial trisomy). This varies from child to child, so generalizations are not possible. Not all characteristics or all characteristics are equally pronounced in all children. The most common features include:
- unusually large amounts of amniotic fluid during pregnancy ( polyhydramnios )
- increased prematurity (before the 37th week of pregnancy)
- retarded growth (already during pregnancy), psychomotor developmental delay
- occasionally asymmetrical growth (body asymmetry, e.g. different lengths of the extremities , displacement of the hips)
- Overlapping fingers or toes
- Heart defects ( Fallot tetralogy above average )
- comparatively small head ( microcephaly ) with a prominent forehead and particularly shaped, deeply set ears, a broad bridge of the nose and occasional facial asymmetry
- long philtrum (hollow between nose and upper lip), cleft palate , unusually arched palate, small lower jaw ( micrognatia ), protruding upper jaw, large mouth opening with full lips (can lead to mouth closure difficulties)
- Deep-set, small, comparatively far apart eyes ( hypertelorism ) with narrow eyelids , the upper eyelids sagging slightly ( ptosis ), translucent film over the eyes
- broad bridge of the nose
- Hyperpigmentation of the skin (increased formation or deposition of skin pigments , which leads to increased coloring of the skin)
- Special features in the urogenital tract in boys: small penis, cryptorchidism (sub-form of undescended testicles)
- Renal failure
- cognitive disabilities of varying degrees of severity
diagnosis
Prenatally, abnormalities in the ultrasound can suggest the presence of a trisomy 14 in the child. Free trisomy 14 and mosaic trisomy 14 can in principle be diagnosed by invasive diagnostic methods such as amniocentesis or chorionic villus sampling . Errors are also possible, especially with chorionic villus sampling: Hahneman and von Vejerslev reported in 1997, for example, three cases of trisomy 14 in chorionic villus sampling: two had no cell mosaic, one did. All three findings only concerned the placenta and could not be detected when examining the cells of the three children. A Locus probe is required to diagnose partial trisomy 14 .
Postnatally, a suspected diagnosis can be made through the evaluation of characteristic physical features, which can be confirmed or excluded by a chromosome analysis.
therapy
The causal healing of trisomy 14 is not possible due to the chromosomal cause, so that the treatment of health-related symptoms (e.g. surgical correction of the heart defect) is in the foreground. Special educational early intervention is helpful for the development of the children.
literature
- B. Dallapiccola, G. Ferranti, A. Giannotti, G. Novelli, L. Pasquini, B. Porfirio: A live infant with trisomy 14 mosaicism and nuclear abnormalities of the neutrophils. In: Journal of Medical Genetics . 1984, Vol 21, pp. 467-470.
- MB Petersen, LO Vejerslev, B. Beck: Trisomy 14 mosaicism in a 2 year old girl. In: Journal of Medical Genetics. 1986, Vol 23, pp. 86-88.
