Wilson disease carrier status, and the one result that is not carrier status
Wilson disease is worth finding, because it is treatable and because untreated it is not survivable. That makes it the odd one out on a carrier panel, and it makes one particular result worth understanding before you meet it.
Also known as: ATP7B carrier, hepatolenticular degeneration, copper storage disease.
- Gene
- ATP7B
- Inheritance
- Autosomal recessive
- Carrier frequency
- about 1 in 90 worldwide
What it is
Wilson disease is caused by changes in ATP7B, the gene for a protein that moves surplus copper out of liver cells, into bile and into the blood. Copper arrives in food and has to leave again. When both copies of ATP7B carry a disease-causing change, it stops leaving, and it accumulates first in the liver and then in the brain. Presentation is unusually varied: liver disease at one end, movement disorders and psychiatric disturbance at the other, sometimes together. So is the timing. The range most people have heard, five to thirty-five years, understates it, and GeneReviews gives untreated presentations from age three to past seventy, which matters if you are older and inclined to rule the condition out on age alone. The disease affects roughly one person in thirty thousand.
What sets it apart from most conditions on a carrier panel is that it responds to treatment. Copper chelating drugs and zinc salts control the accumulation, and GeneReviews is explicit that they are started in everyone with two disease-causing copies, including people who have no symptoms and no detectable organ damage yet. This is why ATP7B appears on the list of genes the American College of Medical Genetics and Genomics recommends reporting when they turn up incidentally: the finding changes what happens next, which is the whole test for that list.
There is an honest complication in the numbers. Population studies keep finding three to four times as many people carrying two ATP7B changes as clinical estimates of the disease predict. GeneReviews raises the obvious question directly, which is whether penetrance is genuinely one hundred percent as usually assumed, or whether some variant combinations are being classified as disease-causing more confidently than they deserve. Either way, two changes found in a file is a reason to be examined by a clinician, not a diagnosis delivered by software.
How it is inherited
Wilson disease is autosomal recessive. A carrier has one changed copy of ATP7B and one working copy, the working copy exports copper, and the result matters for family planning rather than for the carrier's own health: if a reproductive partner also carries an ATP7B change, each pregnancy has a one in four chance of an affected child.
The careful version of that sentence is worth having. GeneReviews says clinical disease is not known to occur in carriers, and then adds that the possibility has not been adequately excluded at older ages. It also notes that carriers can show mild biochemical oddities, a lowish ceruloplasmin, borderline urinary copper, a moderately raised liver copper, and that some of those values overlap the range seen in people who do have the disease. So carrying one change is not a health problem anyone has demonstrated. It is also not quite the flat nothing that consumer genetics copy usually promises, and the biochemical tests are not a shortcut for sorting it out.
There is a second complication, and it is the one that produces the result this page exists for. ATP7B has hundreds of known disease-causing variants rather than one or two common ones, so most affected people carry two different changes rather than the same change twice. A sequencing file that shows two such changes cannot say whether they sit on the same copy of the gene, which would make the person a carrier, or on opposite copies, which would make them affected. That property is called phase, and standard short-read sequencing does not resolve it.
What your raw DNA file can and cannot tell you
Start with the chip file, because for this condition the answer is short. 23andMe publishes the list of conditions its carrier status reports cover, and Wilson disease is not on it. Neither the gene nor the condition is part of what that product reports, so a customer arriving with a 23andMe export has never been told anything about ATP7B. Aimosti does not issue carrier status from a chip file either, for this gene or any other, and says so rather than returning a reassuring blank. The underlying reason is the same one that makes ATP7B hard for arrays generally: the disease-causing variants are numerous and population-specific, with separate founder variants recorded in Sardinian, Ashkenazi Jewish, Canary Islander and Druze populations, so any fixed list of typed positions is informative for some ancestries and close to useless for others.
A whole-genome VCF or gVCF is what our carrier module reads, and it looks across the gene rather than at pre-chosen positions. Here is what our report does with what it finds, because the three outcomes are genuinely different and only one of them is carrier status. One pathogenic change gives a carrier result, filed with the other carrier findings. Two copies of the same change is reported as a clinical finding about you, not a carrier result. Two different pathogenic changes in ATP7B is the third case: the report marks it "Two changes, phase unknown", flags it for attention rather than filing it with the carrier results, and the clinician hand-off states in plain terms that phase is unresolved from unphased data and that the person may be affected. We would rather hand a clinician an unresolved question than resolve it by guessing.
This product is not carrier screening, and it is not a diagnostic pathway for Wilson disease either. The clinical work-up for this condition is largely biochemical, serum ceruloplasmin, serum copper, copper in a twenty-four hour urine collection, an eye examination, sometimes a liver biopsy, scored against criteria agreed at the eighth international meeting on the disease. A re-analysis of a file you already own can tell you that the question is worth asking. It is not a substitute for asking it properly, and if a result here points at two changes in this gene, the next conversation is with a hepatologist rather than with us.
A genotyping chip reads only a few hundred thousand pre-selected positions, about 0.02% of your genome, chosen for common variation. It does not sequence the rest, so it cannot find the rare or novel pathogenic variants the clinical and carrier modules look for: a “no finding” from chip data means “this chip never looked”, far more so than with whole-genome sequencing. Chip data suits common-variant traits, pharmacogenomic tag SNPs, and haplogroup ancestry, not clinical or carrier screening.
Common questions
Does 23andMe or AncestryDNA test for Wilson disease?
23andMe's published carrier status list does not include Wilson disease, so its reports say nothing about ATP7B. That is worth knowing, because Wilson disease is on the professional list of genes worth reporting when they show up incidentally, precisely because it is treatable. A whole-genome file re-analysed against a panel that includes ATP7B can look at the gene; a consumer chip export was never asked to.
My file shows two different ATP7B variants. Am I a carrier or am I affected?
A standard sequencing file cannot tell you, and any product that answers confidently is overreaching. The two changes may sit on the same copy of the gene, which makes you a carrier, or on opposite copies, which means you may have the condition. Resolving that is called phasing and it needs a targeted clinical test, usually alongside the copper measurements that would show whether copper is accumulating. Our report flags this case for attention instead of filing it as carrier status, and it is the one result on this page that should send you to a doctor promptly.
I am a carrier. Should I have my copper levels checked?
That is a question for a clinician who can see your history, not one this page should answer for you. The background: carriers are not known to develop Wilson disease, though the published sources are careful to say the possibility has not been fully excluded at older ages, and carriers can show mild copper-related lab values that overlap the affected range. Those overlaps are why a single ceruloplasmin result does not cleanly sort carriers from patients. What carrier status straightforwardly does mean is that testing a reproductive partner is the useful next step.
If Wilson disease is treatable, why is it reported as carrier status rather than a health finding?
Because one changed copy is not the disease. The treatment exists for people whose copper actually accumulates, which needs both copies affected, and treating a carrier would be treating a laboratory result rather than a condition. The distinction is built into how the report routes the gene: one change goes to the carrier section, two copies of one change or two different changes are handled as findings about you. Same gene, three different answers, decided by what the file shows rather than by which section it was filed under.
Why do more people carry two ATP7B variants than there are Wilson disease patients?
This is an open question in the literature rather than something we can resolve. Population studies have found genetic prevalence running three to four times higher than clinical estimates, which points either to genuinely undiagnosed disease, to variants classified as disease-causing on thinner evidence than the classification implies, or to penetrance being lower than the textbook assumption of complete. It is a good reason to treat a two-change result as the start of a clinical conversation rather than as a verdict.