Heterotaxy

A heterotaxia (Greek heteros , different ', taxis , arrangement') discloses a displacement of the organs in the chest or abdominal cavity from the right to the left side or vice versa. Such malformations are also called lateralization defects . Since there are many possibilities for such a right / left exchange, it is a characteristic of various diseases. A complete exchange is called situs inversus (totalis) and does not actually cause any problems. If only some of the organs are shifted to the opposite side or in the sense of a situs ambiguus in the midline, various heart defects, malformations of the kidneys and biliary tract or so-called midline defects usually occur. All heterotaxies taken together occur in about 1 in 15,000 people.

root cause

Although little is known about the exact cause of this disorder, various genes have now been identified, including ZIC3 , ACVR2B , LEFTY A and CFC1 , which play a role in left-right orientation in embryonic development. However, heterozygous mutations in these genes cause only about 3% of all heterotaxies. The severity of the malformations within affected families varies greatly. Among the hereditary variants of heterotaxies, an autosomal recessive, less often an autosomal dominant and least often an x-linked inheritance were found. The latter are caused by the ZIC3 gene, which is on the X chromosome .

Symptoms

Frequent heart defects that arise in the context of heterotaxia due to a disturbed rotation of the outflow path in the development of the heart are transposition of the large arteries or a double outlet right ventricle . If the heart defect is associated with a lack of the spleen ( asplenia ), one also speaks of the Ivemark symptom complex , named after Björn Ivemark , who first described it . Asplenia is seen as a lateralization defect in which the entire organism has properties of the right half of the body ( right isomerism ). Just as often there are many small spleens (polysplenia), whereby, conversely, the whole body should have the property of the left half of the body ( left isomerism ). Since even organs in pairs are never completely symmetrical, the lungs, kidneys or adrenal glands can also be affected because the symmetry is reversed or completely absent. Midline defects are particularly found in the X-linked mutations in the ZIC3 gene in the form of a lack of the olfactory brain (arhinencephaly), myelomeningocele , cleft palate , anomalies of the urinary tract and malformations of the tail vertebrae and the anus.

Individual evidence

1. ↑ ^{a b c} heterotaxy at www.orpha.net
2. ↑ Hilde Peeters, Marianne L. Voz, Kristin Verschueren, Bart De Cat, Hélène Pendeville, Bernard Thienpont, Ann Schellens, John W. Belmont, Guido David, Wim JM Van De Ven, Jean-Pierre Fryns, Marc Gewillig, Danny Huylebroeck, Bernard Peers, Koen Devriendt: Sesn1 is a novel gene for left-right asymmetry and mediating nodal signaling . In: Human Molecular Genetics . tape 15 , no. 22 , 2006, p. 3369-3377 , doi : 10.1093 / hmg / ddl413 , PMID 17038485 .

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