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Homozygous Familial Hypercholesterolemia (HoFH)
Video

The Importance of Counseling Patients and Families on Genetic Testing for HoFH

Posted on

Eliot Brinton, MD, president of the Utah Lipid Center in Salt Lake City, talks about counseling patients and families on genetic testing for homozygous familial hypercholesterolemia (HoFH).

Question:

Given the hereditary nature of homozygous familial hypercholesterolemia, how would you counsel patients and their families about the genetic implications and the necessity of screening for relatives?

Eliot Brinton, MD:

Whenever we’re dealing with a monogenic disorder, the question arises in terms of genetic testing and gene counseling or genetic counseling. Genetic testing is certainly fine. It’s available, it’s now reasonably routine. But remember that we are still every month discovering new mutations for homozygous FH. There can be a mutation of indeterminate effect or indeterminate or uncertain significance. Gene testing can be done, but it has its limits. I prefer to treat the phenotype because perhaps I’ve got a patient who has a very, very severe case of heterozygous FH where they may need the LDL receptor-independent treatments. If I have proven that they’re heterozygous, then that may get in the way of my being able to use another treatment, especially the 2 medications that are just for homozygous FH. Again, lomitapide and evinacumab are supposedly just for homozygous FH. If I have evidence a patient’s heterozygous, that’s a problem. It’s not a problem in terms of apheresis because then pretty much independent of heterozygous versus homozygous, but that’s one reason for my reluctance. But it can be useful.

If you do genotyping on a patient and you know that they’re homozygous, do you do genetic counseling? I think the quick answer is yes. Here it’s rather simple. It’s a co-dominant disorder. If a homozygote marries a homozygote, then every 1 of their children are going to be homozygous. Please counsel them not to do that. We do well to keep our homozygotes alive long enough to reproduce. In fact, nowadays that’s fairly common. This is not out of the question. Homozygous, if they marry a person who has no genotype of FH whatsoever, and this of course is by far the most common, then each of their children will be heterozygous. But heterozygous FH is relatively straightforward and relatively common and easy to treat. We can make sure they understand this. That’s not a huge problem.

Well, what if a homozygote were to marry a heterozygote or maybe 2 heterozygotes were to marry? If a homozygous and a heterozygous FH patient marry, then every 1 of their children will be at least a heterozygote, and half of their children will be homozygotes. Homozygous FH is a big deal, and I think we need to counsel them in that regard. If a heterozygous marries a heterozygous, then you’ve got the classic situation of 1 in 4 on average will be homozygous. That’s something to be aware of. One in 4 will have no gene at all. They’ll just be normal variety. Then 2 out of 4, half of their kids on average, will be heterozygous FH. Heterozygous FH, it’s 1 in 120 or so of the population. It’s reasonably common. We deal with it all the time. It’s not that severe. Genetic counseling can be done, should be done. This is what we’re looking at in terms of how we might counsel a patient who is homozygous FH in particular, or perhaps heterozygous FH.

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