How to Inherit SMA
Humans have two genes belonging to a trait; one passes from the mother, the other from the father. If one of the genes inherited from the mother and father has changed, the person becomes a carrier. The surrogacy continues for life.
SMA is inherited autosomal recessively. It occurs as a result of survival motor neuron (SMN) protein deficiency. The SMN1 gene encodes the SMN protein.
Individuals with SMA disease have two non-functional copies of the SMN1 gene. Due to the genetic features of the disease, one of the SMN1 gene copies that do not work in 95% of the patients is inherited from the father and the other from the mother. Parents of children with SMA are carriers and do not have the disease. In very rare cases (2%), SMA disease may occur as a result of spontaneous (de novo) errors.
The genetics of SMA disease is quite complex. For this reason and depending on the screening method applied, the screening test may give false-negative information in terms of carriage at a rate of 5%.
The carrier frequency of SMA in the community varies between 1/40-1/60. On average, one out of every 50 individuals in the society is a carrier for SMA disease.
The probability of getting married for two people who are coincidental SMA carriers is very high.
The children of fathers and mothers who are carriers of SMA disease for each pregnancy;
Particularly, consanguineous marriages increase the risk for hereditary diseases due to the high probability of carrying similar diseases within the same family.
What is the Purpose of SMA Carrier Screening?
The purpose of the SMA Carrier Screening initiated by the Ministry of Health across 81 provinces; It is to determine the carrier couples in terms of SMA in the premarital period, to provide genetic counseling to families and to reduce the long-term incidence of SMA disease.
Who Is SMA Carrier Screening Applied to?
SMA Surrogacy Screening is applied to couples who apply to family physicians to get a marriage certificate before marriage, and to couples who are currently married and plan to have a baby.
For the screening, a sample is taken from the male first.
A report is prepared for the applicants for a pre-marriage health report.
The male has a suspicious positive result in the examination results; otherwise, it will be unfollowed. If the male suspects the result; If it does, the screening test should definitely be applied to the woman.
In special cases, simultaneous screening test can be applied to both men and women.
How to Scan for SMA Carriage
Wife/spouse candidates who apply to the Family Medicine Unit to get a pre-marital health report or to have a carrier screening test are informed by the family physician.
For screening tests, blood samples are taken as 2-3 cc in a single tube with EDTA in the Family Medicine Unit where the spouse candidates are registered, barcoded and entered into the system.
Marriage report can be issued to applicants for pre-marriage health report without seeing the screening result.
Tubes, General Directorate of Public Health; It is sent to the Genetic Diseases Screening Laboratory (GHL).
Blood Samples; General Directorate of Public Health; It is tested in the Genetic Diseases Screening Laboratory.
Genetic Diseases Screening Laboratory's study results were reported to the relevant family physician as "normal". or “doubtful” transmitted as People can also see their results via e-pulse.
Resultç “normal” and the spouse/spouse-candidate is informed and removed from the follow-up.
Resultç “doubtful” If so, the screening test is also applied to the wife/wife-to-be.
In the event that both spouses are carriers, a detailed counseling should be given about the risks. Couples, both of whom are carriers, should be referred to a medical geneticist, if there is no specialist in the province, to a medical geneticist in the nearest province/preferred province.
Genetic Diseases Screening Laboratory laboratory results are shown to the medical geneticist via e-pulse with the consent of the applicants.
After the diagnosis is confirmed by a molecular test by a medical geneticist, genetic counseling is given and they are referred to appropriate centers before having a baby.
Carrier couples can have healthy babies: