Proof of genetic deficiency in parents

Question

Hello,

My son is suspected to have CF and is currently being tested accordingly. Since my partner and I are separated, unfortunately I do not have any more detailed information on actual test results from the mother, as she has cut ties with me. I would like to ask anyway whether it is possible for one parent as well to get tested for the genetic deficiency. Is this done through a sweat test as well, or does that only work when one actually has CF?

Thanks in advance.

Answer

Hello,

With an incidence of ca. 1 in 2500 people, cystic fibrosis is one of the most common autosomal recessive hereditary diseases among the Caucasian population. As of now, more than 1600 mutations in the CFTR gene have been described worldwide. In Europe, the main mutation, F508del, can be found in 22-87% of the CF chromosomes, depending on ethnicity. Testing the parents of a CF patient can confirm the mutations that were found in the patient. If the patient is supposed to be homozygous, testing the parents can yield further hints that are important for the human genetic assessment (isodisomy, hemizygosity, compound heterozygosity, etc.). A (tentative) CF diagnosis cannot be ruled out in a patient through molecular genetic testing unless this patient is a clinically suspicious sibling of an affected person with known mutations in the CFTR gene. As a rule, testing of clinically unsuspicious underage siblings of affected persons is not indicated. It does make sense, however, to test patients with a tentative CF diagnosis (which is made based on distinct clinical hints) for the mutations most common in the respective population group in order to confirm the tentative diagnosis. If your son’s CF diagnosis is confirmed, a human genetic consultation is strongly recommended. Clinical tests such as the sweat test you mention are only sensible if you are suspected to have the disease as well.

Kind regards
C. v. Mallinckrodt

15.11.2010