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Did you know your genetics might put you at risk of dry skin?

FLG, the ‘leaky’ skin gene and why it gives you dry skin

There was once a girl who hated summer – the heat, the sun and, most of all, having to wear shorts and skirts. Every summer it was the same story. The stares, the whispers and sometimes the outright pointing, laughing or teasing. It was the dry skin on her legs. It had a pattern that looked like fish scales. She tried telling the kids she had a skin condition, but they just laughed at her and said she didn’t wash enough. The parents were worse. As soon as they heard ‘condition’, they assumed it was contagious. She tried every home remedy she could, but no matter how hard she tried to wash and moisturize, she just couldn’t get rid of the scaly dry skin.

This is the story of someone with ichthyosis vulgaris (IV), also known as the “fish scale disease”. It is a skin condition that results in very dry, flaky skin. IV is an inherited disorder caused by mutations in the FLG gene. This gene encodes the filaggrin protein found in the skin, and the severity of the “fish scales” depends on which mutations have been inherited.

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The skin is the largest organ in our body. It serves as a barrier, protecting us from the environment and guarding against the evaporation of water from inside our body. The impenetrable outer layer of our skin is called the stratum corneum. It consists of 15 to 20 layers of flattened, dead cells.

Filaggrin is key to forming and maintaining the proper structure of this barrier layer. Filaggrin assembles keratin filaments together causing them to collapse down into several layers of skin. These layers are glued together by proteins called transglutaminases, after which filaggrin is broken down and retained to provide our skin moisture. So, when there’s not enough filaggrin, it leads to the production of a “leaky” barrier layer, which increases water loss, leading to dry skin.

There are around 40 known mutations in FLG, and a quarter of them are linked to IV. FLG mutations tend to be population-specific. For example, the first two variants to be linked to IV, rs558269137 and rs61816761, were found in Europeans. Since then, other mutations have been identified in Japanese, Chinese and Korean populations.

Symptoms of IV can be quite variable because it depends on the versions of FLG that an individual inherits. Someone with a variant that only slightly reduces filaggrin levels will only have mild, very localized symptoms, whereas inheriting either rs558269137 and rs61816761, which completely abolish protein activity, can cause moderate to severe IV.

Linking the different variants of FLG to the severity of IV has proven to be tough, mainly because it’s a tricky gene to study. FLG is one of the largest genes in the human genome and contains large regions of repeated DNA sequences. These characteristics make it quite difficult to analyze using existing DNA sequencing methods. Despite these challenges, labs around the world are still determined to study FLG. 

IV is deemed to be the most common skin disorder caused by a single gene. Around 1 in 250 children experience some form of IV. Some of them also suffer from eczema and/or asthma, all of which also linked to faulty FLG. The lucky ones outgrow their condition, as they mature into adults, while others will battle these symptoms all their lives. We can only hope the advent of new technologies, especially in gene sequencing, will make it easier to study FLG. One day maybe we can find a cure so no child will have to suffer the humiliation of being ostracized for their “fish skin”.

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