Eczema and psoriasis share much of their genetics at the same handful of positions — but the risk alleles there point in opposite directions, which is part of why the two diseases almost never occur in the same person.
What this condition connects to
Solid lines are connections this site curates. Dashed lines mean the two ends share a research paper — worth knowing, and not a claim that one explains the other.
Prevalence
A common disease, with prevalence varying substantially by age and population; the largest single genetic study to date combined 21,399 cases with 95,464 controls, later replicated in 32,059 more cases (Paternoster et al. 2015, PMID:26482879).
Inheritance
Polygenic: 14 common variants on this site alone, drawn from a total of 31 loci known genome-wide. FLG (filaggrin) loss-of-function is the single most consistently replicated common risk factor across populations, independently of any one study on this page.
Atopic dermatitis — eczema, in everyday language — is a common, chronic, relapsing inflammatory skin disease, and one of the more genetically mapped diseases of the skin. A large international effort has found 31 associated loci to date; this page holds 14 of them, from four separate studies.
Thirty-one loci, ten of them new in one large study
Paternoster et al. 2015 tested more than 15 million genetic variants in 21,399 people with atopic dermatitis and 95,464 without, across European, African, Japanese and Latino ancestry, then replicated the findings in a further 32,059 cases and 228,628 controls from 18 studies. They found 10 new risk loci, bringing the total known to 31. The new loci point specifically at innate immune defence and T-cell function — the biology of how skin fights off microbes and how immune cells regulate inflammation, both directly relevant to a disease that is, underneath the itch, an immune-barrier problem.
Two further studies, in Japanese and Chinese Han populations, contributed more of this page's loci and independently replicated several already-known Western loci in East Asian samples — including FLG, the gene for filaggrin, a structural protein that helps build the skin's outer barrier. Filaggrin loss-of-function is, independently of any single study here, the most consistently replicated common genetic risk factor for atopic dermatitis across populations, and is part of why eczema often runs alongside asthma and other allergies later in life — the so-called "atopic march."
Eczema and psoriasis: the same loci, pointing opposite ways
Atopic dermatitis and this site's psoriasis page are the two most common immune-mediated inflammatory skin diseases, and a direct genome-wide comparison of more than 19,000 people found something specific: the two diseases share substantial genetic architecture at the same regions — the epidermal differentiation complex, the Th2 immune-regulation region, and the major histocompatibility complex — but the risk allele at each shared position runs in opposite directions between the two diseases. Two more shared loci with the same opposing pattern, near PRKRA and ANXA6/TNIP1, were newly identified in that same comparison.
This lines up with something dermatologists already knew clinically: atopic dermatitis and psoriasis very rarely occur in the same person, despite drawing on much of the same genetic and immune machinery. rs41268896, one of this page's variants, sits in the major histocompatibility complex region this comparison studied directly.
Clinical detail
What is actually diagnosed and treated here
Atopic dermatitis is diagnosed clinically, from the appearance and history of the rash, not from a genotype. None of the 14 variants on this page are used by any guideline to diagnose eczema or predict its severity in an individual.
The loci described above are population-level GWAS findings from tens of thousands of people. They explain part of why atopic dermatitis clusters in families and why it shares underlying biology with related allergic and immune conditions — they do not predict whether, or how severely, any one person will develop it.
Related variants MyGeneLog™ checks for
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Atopic Dermatitis comes down to these specific, well-studied positions — not a diagnosis. 80 positions are linked to this page; the ones this page's own text discusses are shown first.
The studies behind these variants recruited participants from different ancestries — a result found in one population doesn't always transfer to another. Based on 14 of 80 linked studies with a resolved discovery ancestry.
16.2%
European · 1.2% East Asian · 16.2% Not yet resolved · 82.5%
Atopic dermatitis — eczema — is a common, chronic, relapsing inflammatory skin disease. It is one of the more genetically mapped skin diseases, with 31 associated loci known to date.
What is the single most important atopic dermatitis gene?
FLG, the gene for filaggrin, a structural protein in the skin barrier. Filaggrin loss-of-function is the most consistently replicated common genetic risk factor for atopic dermatitis across populations, and is part of why eczema often precedes asthma and other allergies.
Why does this page link to the psoriasis page?
A direct genome-wide comparison of more than 19,000 people found that atopic dermatitis and psoriasis share much of their genetic architecture at the same regions, but the risk allele at each shared position runs in opposite directions between the two diseases — matching how rarely the two conditions occur in the same person.
Can these variants predict whether I will get eczema?
No. Atopic dermatitis is diagnosed clinically, from the rash and its history. These are population-level findings from tens of thousands of people, not a way to predict an individual case.
Free to reuse. This page's text is original writing from freely-available research, licensed CC BY 4.0 — reuse it, including commercially, with attribution to MyGeneLog™. It's general research-derived information, not medical advice or a diagnosis — see Terms of Use.