What Is the True Prevalence of Fabry Disease?

Fabry disease is an inherited condition that was long counted as very rare, but how rare depends on how you count. Tallying only the people doctors have diagnosed gives a small number, while testing every newborn finds gene changes many times more often.1bioRxiv. Estimating the prevalence of late-onset Fabry disease in the US in 2024 The true figure is less a single number than a gap between people who are diagnosed and people who carry the change but may get sick late, mildly, or not at all.

The Two Sets of Numbers You Will Find

The older figures come from counting diagnosed patients. Those counts put Fabry disease at about 1 in 40,000 to 1 in 170,000 people.2bioRxiv. Estimating the prevalence of late-onset Fabry disease in the US in 2024 The classic form alone has been estimated at about 1 in 50,000 boys.3PubMed Central. High incidence of later-onset fabry disease revealed by newborn screening Even these sources note that the real number may be higher, because many people are diagnosed late in life.4CareConnect. Diagnosis and testing of Fabry disease

Newborn screening gives a different picture:

The two sets of numbers count different things. A case-based figure counts people whose disease was recognised, usually because they became ill. A screening figure counts babies who carry a gene change or have a low enzyme level, whether or not they will ever be ill.

Units differ too. Fabry is X-linked, so boys and men are most often affected, and many screening studies report only on boys. A “per boy” figure shouldn’t be set beside a “per person” figure without adjusting for that. Studies also differ in method: some measure enzyme activity, others read the GLA gene, and the two approaches can flag different babies. So check who was counted before comparing numbers.

Classic and Later-Onset Fabry Are Not Equally Common

Fabry disease comes from changes in the GLA gene on the X chromosome, which makes an enzyme that breaks down certain fats.9PubMed Central. An Overview of Molecular Mechanisms in Fabry Disease Without enough working enzyme, fatty substances build up in blood vessels and organs throughout the body.10PubMed Central. An Overview of Molecular Mechanisms in Fabry Disease Over years, this damages the heart, kidneys and nervous system.11PubMed Central. An Overview of Molecular Mechanisms in Fabry Disease

Classic Fabry disease is the early, multi-organ form, and it often starts around age 6 in boys and 9 in girls.12Rare Disease Advisor. Fabry Disease Epidemiology Early signs include burning pain in the hands and feet, stomach problems, small dark skin spots, and reduced sweating.13PubMed Central. Fabry disease in females: organ involvement and clinical outcomes compared with the general population Later it can lead to heart thickening, stroke and kidney disease.14PubMed. When and How to Diagnose Fabry Disease in Clinical Pratice

Later-onset Fabry disease is the milder form, and it is far more common. In the Italian newborn screen, later-onset cases outnumbered classic cases about 11 to 1.15PubMed Central. High incidence of later-onset fabry disease revealed by newborn screening So most of the extra cases screening finds are the later-onset form. In Taiwan, one later-onset gene change alone appeared in about 1 in 1,460 baby boys.16PubMed Central. Newborn Screening for Fabry Disease in Taiwan Reveals a High Incidence of the Later-Onset Mutation c.936+919G>A (IVS4+919G>A) This change leaves around 10% of normal enzyme activity and mainly affects the heart later in life.17PubMed Central. Newborn Screening for Fabry Disease in Taiwan Reveals a High Incidence of the Later-Onset Mutation c.936+919G>A (IVS4+919G>A)

In adults, the later-onset form often shows up in middle age or later rather than childhood. It usually affects one organ, most often the heart, instead of many. People may never have had the childhood pain or skin spots, so it can be mistaken for the ordinary heart or kidney disease of ageing. Someone with classic Fabry may need treatment in childhood, while someone with the later-onset form may stay well into adulthood. When you read a prevalence figure, check whether it is for the classic form, the later-onset form or both.

How Common It Is Among People With Heart, Kidney or Stroke Problems

Among Europeans with unexplained heart-muscle thickening, about 0.5% had a disease-causing Fabry change.18PubMed. Prevalence of Anderson-Fabry disease in patients with hypertrophic cardiomyopathy: the European Anderson-Fabry Disease survey In small studies of men with heart thickening that started later in life, 3% to 6% had Fabry.19PubMed Central. Cardiac manifestations of Fabry disease But one study’s 4.7% fell to 0.9% once a single common family gene change was set aside.20PubMed. Predictors of Fabry disease in patients with hypertrophic cardiomyopathy: How to guide the diagnostic strategy? When patients had several warning signs, such as heart rhythm problems or certain ECG findings, the rate rose to nearly 1 in 5.21Journal of Human Genetics. Fabry disease in patients with hypertrophic cardiomyopathy: a practical approach to diagnosis

In a Russian nationwide screen of dialysis patients, about 0.5% of men and 0.05% of women had Fabry.22PubMed Central. The Prevalence and Clinical Features of Fabry Disease in Hemodialysis Patients: Russian Nationwide Fabry Dialysis Screening Program A large UK dialysis screen, though, found no new cases at all.23PubMed Central. Fabry disease in the haemodialysis population: outcome of a UK screening study (SoFAH)

For stroke in younger adults, studies of stroke without a clear cause found Fabry in about 1.3% of patients overall.24PubMed. Prevalence of Fabry disease in cryptogenic stroke: a systematic review and meta-analysis with meta-regression Individual studies found 0.3% or none.25PubMed. Prevalence of Fabry Disease and Outcomes in Young Canadian Patients With Cryptogenic Ischemic Cerebrovascular Events

These percentages vary so much because each study picked patients differently, from broad to tightly selected. Some countries have common family gene changes that push numbers up, and studies disagree on which gene changes count as disease.

The word “unexplained” matters. These figures apply to people whose organ problem had no clear cause after standard checks, not to everyone with heart, kidney or stroke disease. Most people with thickened heart muscle, kidney failure or stroke have common causes such as high blood pressure, diabetes or other inherited heart conditions, so Fabry is a rare explanation even in these groups. It is worth considering only after the more usual causes have been looked at and do not fit. For any one patient, Fabry is unlikely, and a negative result is the expected outcome.

It makes sense to ask your doctor about testing if you have heart thickening, kidney failure or stroke at a young age without a clear cause. Other clues alongside it, such as high-pitched hearing loss, fainting spells or gut bleeding, strengthen the case, as does a relative with Fabry or with similar unexplained problems. Ask which test is suitable; a gene test is especially important for women, whose enzyme results often look normal.

Why a Gene Change Is Not Always Fabry Disease

In high-risk groups, about 0.62% carry a GLA variant, but only 0.12% have definite Fabry disease.26PubMed. A systematic review on screening for Fabry disease: prevalence of individuals with genetic variants of unknown significance So roughly 4 in 5 people with a variant in those groups do not have confirmed disease. Most people found through newborn and high-risk screening carry uncertain or harmless variants.27PubMed. A systematic review on screening for Fabry disease: prevalence of individuals with genetic variants of unknown significance

A variant is a spelling difference in the GLA gene. Some differences stop the enzyme working, while others leave it working normally. Scientists sort variants by combining enzyme results, lyso-Gb3 levels, tissue findings and what happened to relatives who carry them. When that evidence is thin, the lab may call the change a variant of uncertain significance on your report: it has been seen, but its effect is not yet known.

A few variants cause most of the disagreement. Estimates change depending on which variants experts call disease-causing, and three variants (A143T, D313Y, E66Q) account for most disputes.28PubMed. Impact of GLA Variant Classification on the Estimated Prevalence of Fabry Disease: A Systematic Review and Meta-Analysis of Screening Studies D313Y is now classed as harmless by US labs, and a study of over 38,000 samples found no link to disease.29PubMed Central. A Retrospective Cohort Study of the GLA c.937G > T, p.Asp313Tyr Variant With No Evidence of an Association With Fabry Disease People with D313Y can also show falsely low enzyme results in blood plasma.30PubMed Central. A Retrospective Cohort Study of the GLA c.937G > T, p.Asp313Tyr Variant With No Evidence of an Association With Fabry Disease If a study counts every variant as Fabry, its prevalence rises sharply; if it counts only proven disease-causing variants, the figure falls.

To decide, doctors often check lyso-Gb3, a blood marker of the fat build-up, which is high in classic disease.31PubMed Central. Elevated globotriaosylsphingosine is a hallmark of Fabry disease In one study it was normal in everyone carrying D313Y or other uncertain and harmless variants, though it can be only mildly raised or normal in some later-onset disease.32PubMed Central. A Retrospective Cohort Study of the GLA c.937G > T, p.Asp313Tyr Variant With No Evidence of an Association With Fabry Disease

If your report says variant of uncertain significance, it means the lab cannot yet say whether the change causes disease. Ask for the exact variant name and whether it has been reclassified. Ask whether lyso-Gb3, an enzyme test or organ checks were done. A genetic counsellor can help interpret the result for your family.

Fabry Disease in Women

Because the gene sits on the X chromosome, women were long thought to be mostly healthy carriers.33PubMed Central. X Chromosome Inactivation in Carriers of Fabry Disease: Review and Meta-Analysis Yet about 70% of women with a disease-causing change have symptoms, from very mild to severe.34PubMed Central. X Chromosome Inactivation in Carriers of Fabry Disease: Review and Meta-Analysis Women with the classic form usually develop symptoms in childhood or the teenage years.35PubMed Central. Fabry disease in females: organ involvement and clinical outcomes compared with the general population

The word “carrier” misleads here. It suggests someone who passes on a gene but stays well, which is not true for most women with a disease-causing Fabry change. Women can develop heart, kidney or nerve problems and may be told their symptoms are unrelated to the family diagnosis. Used loosely, the label can delay checks that would otherwise be arranged.

Symptoms vary widely because each cell in a woman’s body switches off one of her two X chromosomes at random. Some cells use the working GLA copy and others use the changed copy. The mix differs from woman to woman and from organ to organ, so one woman may have severe disease and another none, and sisters with the same change can have very different experiences.

Women are also undercounted. Enzyme tests often look normal in women, so they miss many cases.36PubMed. A comprehensive testing algorithm for the diagnosis of Fabry disease in males and females For women, a gene test plus lyso-Gb3 is the most reliable first step.37PubMed. A comprehensive testing algorithm for the diagnosis of Fabry disease in males and females In nearly 29,000 women screened after unexplained heart, kidney or stroke events, relying on enzyme tests led to many missed diagnoses.38PubMed Central. A Meta-Analysis to Unveil the Diagnostic Gaps in Anderson-Fabry Disease in Women

For a woman in a Fabry family, a normal enzyme test does not rule her out. She can request a gene test if a relative has a known variant. Women tend to be diagnosed and treated later than men, which is a reason not to wait.

Why So Many People Go Undiagnosed

Children’s pain is often called growing pains.39PubMed. Common Misdiagnoses for Fabry Disease: The Diagnostic Odyssey Adults are often told they have multiple sclerosis, irritable bowel syndrome or ordinary heart disease.40PubMed. Common Misdiagnoses for Fabry Disease: The Diagnostic Odyssey Diagnosis can be delayed by up to 15 years.41PubMed Central. Fabry Disease in Women: Genetic Basis, Available Biomarkers, and Clinical Manifestations

The symptoms are common ones such as pain, stomach upset, tiredness and heart or kidney trouble, and each can be given its own ordinary cause. Different organs are often managed by different specialists, so nobody sees the whole pattern at once. Doctors rarely meet Fabry, so it is seldom the first thing they think of.

People who die or reach kidney failure without a diagnosis never appear in case counts. Counts also depend on how many doctors in a country know to test, so a region with more awareness will report higher rates.

Some clues point toward Fabry rather than a common illness: burning hand and foot pain, often triggered by heat, exercise or fever; little or no sweating and poor heat tolerance; small dark red spots, often around the hips or navel; and several relatives with early heart, kidney or stroke problems.

At an appointment, bring a list of symptoms going back to childhood, even minor ones. A family tree noting kidney failure, strokes or heart problems helps, as do any earlier test results mentioning enzyme or gene findings.

Does Finding More Cases Early Help

Damage from late diagnosis often cannot be undone.42PubMed Central. Fabry Disease in Women: Genetic Basis, Available Biomarkers, and Clinical Manifestations But enzyme replacement therapy started before symptoms has lowered lyso-Gb3 to undetectable levels in children with classic disease.43PubMed Central. Early initiation of enzyme replacement therapy in classical Fabry disease normalizes biomarkers in clinically asymptomatic pediatric patients So early treatment may prevent heart, kidney and nerve damage.44PubMed Central. Early initiation of enzyme replacement therapy in classical Fabry disease normalizes biomarkers in clinically asymptomatic pediatric patients

What “early” means differs by form. In classic disease, it means treating before or soon after organ damage starts, which can be in childhood or the teenage years. In later-onset disease, it usually means finding the change so monitoring can begin, not starting treatment right away.

Screening has drawbacks. Finding later-onset forms at birth can cause parents lasting worry.45PubMed Central. Newborn Screening for Fabry Disease: Current Status of Knowledge Such children risk becoming “patients in waiting,” labelled and overtreated.46PubMed Central. Newborn Screening for Fabry Disease in Northeastern Italy: Results of Five Years of Experience Still, parents of babies with later-onset forms can be told to expect a normal childhood, with regular checks to decide if treatment is ever needed.47PubMed Central. Newborn Screening for Fabry Disease in Northeastern Italy: Results of Five Years of Experience

After a later-onset newborn result, follow-up typically means regular check-ups of heart, kidneys and blood markers over the years, with no treatment unless signs of organ involvement appear. Testing other relatives, especially the mother, may be offered, and emotional support for parents is part of good care.

The same screening result can lead to different plans. A baby with a classic-type change and high lyso-Gb3 may be offered treatment sooner, while a baby with a later-onset change is usually watched. Doctors weigh the specific variant, lyso-Gb3, enzyme level and family history together.