<<NECESSARY TESTS IN PREGNANCY>>
Cystic Fibrosis (CF) is the most common genetic disease in the white CaucasianCystic Fibrosis (CF) is the most common genetic disease in the white Caucasianpopulation, with serious consequences for the health and life of the affected child.
The disease is caused by damage to the CFTR gene, it is hereditary and is transmittedThe disease is caused by damage to the CFTR gene, it is hereditary and is transmittedin the recessive mode of inheritance, i.e. people who have the damage on one of thetwo chromosomes are said to be carriers and do not suffer, while in order to suffersomeone must have inherited the damage from both parents (25% probability). Thefrequency of carriers of the disease in the Greek population is about 1 in 25 andevery year about 50 affected children are born in Greece. The disease usuallymanifests itself early in infancy although it is sometimes not immediately recognized.The mucous glands of the body are mainly affected, with the result that bodilysecretions become thick and thus block the ducts or airways of many organs, such asthe lungs, pancreas and liver. In men, specific disease mutations can cause infertility.
He "sweat test" is usually applied to newborns and young children who arehe "sweat test" is usually applied to newborns and young children who aresuspected of being sick, and of course full confirmation can only be done withmolecular genetic testing.
The particular problems with fibrocystic disease are twofold: (a) carriers areThe particular problems with fibrocystic disease are twofold: (a) carriers areperfectly healthy, with no symptoms and therefore no way to identify them, and (b)the gene is relatively large in size with many possible mutations (>1300) .
Furthermore, mutations in the gene are not the same in frequency in all populations,Furthermore, mutations in the gene are not the same in frequency in all populations,with very significant differences, for example, between peoples of Northern Europeand the Mediterranean.
The only way to identify carriers of fibrocystic disease is by molecular genetic testingThe only way to identify carriers of fibrocystic disease is by molecular genetic testing(detection of mutations in the CFTR gene) in the general population (carrier detection).
In many countries now, with specific guidelines that have beenIn many countries now, with specific guidelines that have beenissued, molecular genetic testing for fibrocystic disease is recommended in allcouples (usually the mother is tested first), before pregnancy or very early inpregnancy (WE NEVER TEST THE FETUS DIRECTLY).
The most basic element of this control is the percentage of mutations to be detectedThe most basic element of this control is the percentage of mutations to be detectedin the specific population. Due to the large number of mutations and also thedifferent frequency of mutations in different populations-ethnicities, it is almostimpossible to design a specific group-number of mutations to be tested worldwide.
For this reason, it is recommended, with international guidelines, to test geneFor this reason, it is recommended, with international guidelines, to test genemutations that cover ~85% of all mutations in the given population. In prenataltesting, and especially in high-risk cases (e.g. ultrasound-guided bowel and P508abI carrier fetus), then it is desirable to immediately test the PARENTS (and not thecarrier fetus), then it is desirable to immediately test the PARENTS (and not thefetus), which covers the greatest possible percentage of mutations. In case, ofcourse, it is already known that both parents are carriers, then it is necessary (andrelatively simple) to check the fetus, which has a 25% chance of being affected. 1 in700 couples are CF BOTH carriers of the disease, with a 25% chance of havingaffected children If the mother was NOT detected with a mutation (with 85%detection), then the risk of having an affected child (without testing the father) is~1/17000.
1.If a mutation is found in the mother (she is a carrier-heterozygote), then the risk of1. If a mutation is found in the mother (she is a carrier-heterozygote), then the risk ofhaving a sick child (without the father being tested) is about 1/100. After testing thefather with 85% detection and NO mutation found, the risk drops to about 1/700. Ifthe father is tested with ~95% detection and NO mutation is found, then the riskdrops even further to 1/1000.
Disclosure of the specific genetic lesion associated with fibrocystic disease is aDisclosure of the specific genetic lesion associated with fibrocystic disease is avaluable (if necessary) tool for further management of the case by the referringphysician. Without this knowledge, it is difficult to give genetic counseling for thedevelopment of the patient or the fetus, for the reproductive choices of the coupleand for the general effects on the family.
