CF Gene and MTHFR

[nanoffour]

I am 51 and earlier this year was hospitalized for 5 emboli.  As far as I know there is no family history of such occurances.  DNA testing indicated I was heterozygous for the C677T mutation.  According to my PCP I will be going through further testing in October.  However, 3 weeks ago, my oldest son and Daughter-in-law gave birth to their first child.  Today, she was diagnosed with Cystic Fibrosis.  It was recommended my three other children be tested for the recessive gene.  Does my genetic testing of MTHFR have anything to do with passing the recessive gene on to my son, who in turn passed it on to his daughter?

[Jordanna Joaquina, MS, CGC]

We hope your granddaughter is doing well and that she is getting the care she needs. We hope your family is getting the support and resources they need as well.

MTHFR is gene located on chromosome 1 at the location p36.3. We all have two copies of this gene. C677T refers to a variant of this gene. People who are heterozygous for C677T, have one copy with the variant and one normal copy of the gene. People who are heterozyous have a 50% chance to pass on this variant to each child they have. We recommend that follow-up with your PCP regarding your follow-up testing.

Cystic fibrosis (commonly called CF) is a separate genetic condition that affects the mucus and sweat glands. CF causes mucus to be thick and sticky, which in turn gets stuck and causes obstructions in the affected organs and tissues. Some of the major affected organs are the lungs, pancreas, and sex organs.

Cystic fibrosis is caused by mutations in a gene called CFTR on the chromosome 7 at the location q31.2. We all have two copies of the CFTR gene. As you already know, CF is an autosomal recessive condition, as two mutations (one from each parent) are typically necessary to cause the disease. Carriers typically do not have any symptoms.

CF is more common in Caucasians - about 1 in 25 are carriers. Therefore, your son could have inherited his CF mutation from either of his parents and he may or may not have inherited the MTHFR variant. We recommend that you and your children meet with genetics to review the family history and discuss the benefits and limitations of genetic testing for both MTFHR and CF. You can find a medical geneticist at the American College of Medical Genetics website. You can find a genetic counselor at the National Society of Genetic Counselors website or through companies like mine, AccessDNA. You can also find more info on MFTHR and CF through AccessDNA.