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Situs Inversus


Clinical types

Full (complete) situs inversus - the heart and abdominal organs are completely reversed, i.e. the apex of the heart and the stomach are on the right.

Partial (incomplete) situs inversus - the heart is on the right but the liver is usually in the center of the body. There are two main types:

  1. One where both sides of the body resemble the left side.

  2. One where both sides of the body resemble the right side.

These are called respectively left and right isomerism sequence.

Limited situs inversus with an inversion of the stomach only - rare.

Situs inversus as part of Kartagener syndrome - approximately 20% of cases of full situs inversus are Kartagener syndrome.

Clinical signs

Full situs inversus - the heart and abdominal organs are completely reversed, i.e. the apex of the heart and the stomach are on the right. This condition is not usually associated with accompanying defects, although some studies have reported associated heart defects that are evident on ultrasound examination. In the absence of a heart defect, there are usually no other problems, but a few cases of blockage of the biliary tract have been described. This is apparently the more common type, occurring in 1 out of every 6,000 births. It is estimated that up to about 20% of these cases are Kartagener syndrome (see below).

Partial situs inversus - the heart is on the right but the liver is usually in the center of the body. There are two main types:

  1. Both sides of the body resemble the left side (left isomerism sequence). Here there are bilateral long bronchi and bilateral bilobed lungs, i.e. each lung has two lobes whereas in a healthy individual this is only the case in the left lung. This condition is associated with congenital failure of development of part of the inferior vena cava. Multiple spleens often develop. Some of the heart defects are associated with increased blood flow to the lungs and the resultant engorging of the lungs with blood. There are also defects in the digestive tract including incorrectly situated intestines, intestinal blockages, etc., and blockages of the bile ducts in the liver.

  2. Both sides of the body resemble the right side (right isomerism sequence). Here there are bilateral short bronchi and bilateral trilobed lungs, i.e. each lung has three lobes whereas in a healthy individual this is only the case in the right lung. This condition is also associated with agenesis of the spleen and many other defects. Heart defects are associated with inadequate blood flow to the lungs and marked absence of blood vessels in the lungs. There are also defects in the digestive tract including incorrectly situated intestines, intestinal blockages, etc., and blockages of the bile ducts in the liver.

    Both these types may also involve additional defects, such as cleft palate, defects in the closure of the spinal column, blockages of the airways in the nose, which can, however, be opened immediately after birth, clubfeet, etc.

Limited situs inversus in which there is inversion of only the stomach is rare.

Situs inversus as part of Kartagener syndrome. Kartagener syndrome is a group of diseases caused by lack of motility of the cilia on the cells of the lining of the respiratory tract and a disorder in the motility of sperm cells.

In the airways the disease manifests as recurrent (chronic) sinusitis, recurrent ear infections and chronic respiratory tract inflammation, including damage to the walls of the lungs and chronic infection of the damaged region (bronchiectasis).

The defect in this condition is caused by a lack of the substance that provides the cilia with the energy they need, called dynein.

Due to this, there is a reduction or absence of ciliary motility.
This leads to a severely reduced ability to evacuate phlegm, particles and infective pathogens using the cilia, which in turn leads to an accumulation of bacteria, and later to all the complications listed above. The frequency is 1 in 20,000. Diagnosis is made by examining the cilia under an electron microscope in order to confirm the absence of the characteristic dynein arms in the cilia, and to provide a quantitative examination of the ciliary motility. The prognosis is significantly better than that of diseases such as cystic fibrosis, and if effectively treated, the subject's life expectancy is normal. Recently, in vitro fertilization involving the injection of sperm cells into ova has commenced- this ensures that Kartagener syndrome patients remain fertile.

Inheritance pattern

Most cases of situs inversus, with the exception of Kartagener syndrome, are sporadic, without a tendency for recurrence in subsequent pregnancies. In these cases, there may be a spontaneous (new) mutation or involvement of a number of genes in conjunction with environmental conditions that together determine whether the disease appears. A number of different genes involved in the process of determining the normal direction of intrauterine development have been found - damage in these can lead to situs inversus. There are a few cases with autosomal dominant inheritance, and in these the risk for recurrence is 50% in every pregnancy.

Kartagener syndrome has clear autosomal recessive inheritance - the risk of recurrence in a couple who has already had a child with this condition is 25% in every pregnancy.

Penetrance

In Kartagener syndrome patients, situs inversus occurs in only 50% of cases.

Associated features that can be demonstrated by imagery

Fetal ultrasound examination may reveal abnormalities in the locations of the heart, stomach, and liver. It may also be possible to see heart defects and polyhydramnios on ultrasound, and maybe failure to demonstrate a gallbladder. Hyperechogenic intestines and clubfeet, etc. may be seen.

What is the risk of recurrence in subsequent pregnancies?

The regular risk in the population is about 1 in every 6,000 pregnancies.

Parents who have had a child with this condition have a risk of up to 50%.

In Kartagener syndrome, the risk for recurrence of a couple with an affected child is 25% in every pregnancy.

Molecular genetic information

The genes for the disease

Different and diverse genes associated with situs inversus of the various types are known. It is difficult to identify them at the present time.

A gene known as DNAI1 that is responsible for about 15% of cases of Kartagener syndrome has recently been found. There are apparently other genes that can also cause this syndrome. The mutations in the gene that have been found up to now in Kartagener syndrome patients are all in the same region of the gene, so it is relatively easy to test for them.

Location

The gene DNAI1 is situated on chromosome 9p13.

Genetic testing

Diagnostic testing

There are to date no clinical genetic tests for diagnosing this condition. Only in families with multiple cases is it possible to carry out investigations that may lead to the possibility of performing practical tests in some families in the future, initially by indirect tests (linkage analysis), and in the more distant future, once the gene itself has been found, by identifying the mutation or mutations. This will be done in cooperation with a genetic institute. See information sheet: Indirect testing for genetic markers in a family that has one or several patients - when there are a number of different genes that can each cause the disease - the gene, or most of the genes not having been located / identified / mapped - multifactorial diseases

In Kartagener syndrome it is possible to look for mutations in the gene that has been found, DNAI1. A normal test, however, does not rule out this condition, as the gene is responsible for only 15% of cases - in the others, a different gene is involved.

Carrier testing

This cannot usually be performed. See above under diagnostic testing.

Fetal testing

This cannot usually be performed. See above under diagnostic testing. Ultrasound detection as stated above is possible.
 
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Comments (4)


Tuesday, August 23, 2011 1:41 PM
(1) kylasandra O'Hea  says:


pregnancy while having full situs inversus

as informative as the site is, my main concern or question about situs inversus is, is it possible to get pregnant and or carry full term, i have full situs inversus, all organs and heart is reversed and do have lung ear and nasal issues reoccuring quite often in a year, i would liek to start a family but realize been a bit difficult to do so let alone go father than 2 months of pregnancy before miscarrying


Thursday, October 20, 2011 9:42 AM
(2) farrey  says:


pregnancy with situs inversus totalis and dextrocardia

I recently found out I hve situs inversus totalis with dextrocardi and have had no health problems. I am 31 years old with a very healthy 1 and half year old baby girl. It was a very normal pregnancy. I too had a miscarriage once before this baby. It is nothing to do with your condition. SO go ahead and start your family. All the best!!!


Sunday, April 29, 2012 11:07 PM
(3) Aida  says:


Pregnancy full situa in versus totals

Have 2 healthy boys, with natural birth, healthy labours. O miscarriages, thank God. god bless and good luck


Tuesday, February 11, 2014 8:04 AM
(4) Ann  says:


Pregnancy - Total situs inversus

I have total situs inversus. I have 3 healthy children and they don't have situs inversus.





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