National Scarring Alopecia Awareness Month (Day 28, Myth 13). Are scarring alopecias inherited?

On the Concept of “Genetics” for Scarring Alopecia

If mom is tall and dad is tall, the children of these parents are probably going to be tall. That makes sense.

But if mom does not have scarring alopecia and dad does not have scarring alopecia, and nobody at the family reunion last summer said they ever heard of something called a scarring alopecia, how is it even possible to say that genetics is in some way involved if a child grows up to someday develop scarring alopecia.

Well, there are certain genes that people inherit that seem to “predipose” to developing some autoimmune conditions.

It’s also possible that if two people inherit certain genes, one might get one type of autoimmune condition and another person will get another type of autoimmune condition.

Some scarring alopecias have a clear genetic link for some people. For example, central centrifugal cicatricial alopecia may be passed down the family tree in some families - but not all. A 2019 study showed that genes encoding a protein known as PADI3 are know to contribute to some cases of CCCA. Not all cases are thought to involve this gene but up to one-third might be.

A 2019 study also uncovered that four genes increase the risk of frontal fibrosing alopecia. The challenging concept to grasp is that even if one has an “FFA gene” the chances of developing FFA is still very low. For example, the risk of FFA might be 1;6000 in the general population but move up to 1:1000 to 1:1500 if a person has one of these FFA genes. There is still a 99.9 % chance that a person who has these newly discovered FFA genes won’t ever develop FFA.

In summary, there is a role for genetics in scarring alopecia but the inheritance patterns are not the straightforward genetics we are used to when we discuss our family tree. It may be that certain genes increase the risk a little bit to developing scarring alopecia. One of the most strongly linked to “genetics” is CCCA, followed by frontal fibrosing alopecia, lichen planopilaris, discoid lupus.

REFERENCE

Christos Tziotzios et al. Genome-wide association study in frontal fibrosing alopecia identifies four susceptibility loci including HLA-B*07:02. Nature 2019. Online March 8, 2019

Malki et al. Variant PADI3 in Central Centrifugal Cicatricial Alopecia. New Engl J Med. 2019 Feb 28;380(9):833-841.