If you are an individual with Fabry disease or a family member, knowing how many people have Fabry disease is probably not that useful but it’s interesting.
To researchers, policy makers, drug suppliers, investors, businesses that provide support to care, etc. the number is probably much more useful.
The numbers reported are usually discussed in at least three ways: Incidence, prevalence and the number of people affected.
Incidence (rate of appearance): the number of new cases in a given period of time (day, month, year). Fabry disease newborn screening is a good example. The 2013 six-month, full-state population screening in Missouri revealed a Fabry gene mutation detection rate of a staggering one in 2,913 newborns. Ongoing research indicates many of these detected gene mutations may not cause Fabry disease symptoms but there will still likely be many more people with classic and non-classic Fabry disease than historical estimates indicate.
Prevalence: the proportion of cases at a specific point in time. It is usually expressed as a fraction, a percentage or a number per 10,000 of 100,000 people, etc., such as the commonly used U.S. estimate for Fabry disease described in the National Institutes of Health Genetics Home Reference which states “Fabry disease affects an estimated 1 in 40,000 to 60,000 males.” This enables one to calculate an estimate of how many people have Fabry disease at any point in time. But the math is not easy for all categories of people with Fabry (males with a classic mutation, females with a classic mutation, males with a non-classic mutation, females with a non-classic mutation, people with a non-disease causing mutation).
Why are the numbers usually quoted in terms of males? What about females, they are affected also?
The statistics are often quoted in terms of males because with an X-linked inheritance pattern, the estimated numbers of males with Fabry disease are easier to determine.
The bottom line: The number of people that have Fabry disease is a very difficult number to calculate. No one really knows how many people are affected but here is one possible scenario.
Here is an estimate of the U.S. population using the prevalence of 1 in 40,000 to 60,000 (average 1 in 50,000) males cited by the National Institutes of health.
The estimated U.S. population in 2016 is about 323 million people. The percentage of males and females per year is usually about 50% each.
Estimated males with classic Fabry disease: Half of 323,000,000 people equals 161,500,000 males. Therefore, males with FD equals 161,500,000/50,000 for a total of 3,230 males in the U.S.
Genetic math states twice as many females inherit an X-linked gene as males which equals about 6,460 females with the Fabry gene in the U.S.
A 2008 study1 of 1077 females in the Fabry Registry indicated 69.4% females had symptoms and signs of Fabry disease. This yields an estimate of about 4,483 affected females and a total estimated U.S. Fabry population (males and females) of 7,713 based on the current prevalence rate. Only about 4,000 to 5,000 people are known in the U.S. so far.
Now consider the 2013 Missouri newborn screening result with a 1 in 2,913 detection rate applied to the entire U.S. population of 323 million people.
323,000,000/2,913 is about 110,882 people with a Fabry gene mutation. Even if only 25% of those detected have a mutation that causes symptoms, the estimated population would be about 27,720 people with classic and non-classic Fabry disease in the U.S. alone.
Please do not quote these numbers as proven population numbers but they represent a very real possibility and may still be very conservative numbers. Many in the Missouri study will likely have a non-classic form of disease (which could still cause significant symptoms especially heart and kidney problems) or a non-disease causing form of the Fabry mutation. More to come!
Bottom line: We suggest there are thousands of people unknowingly living with classic and non-classic Fabry disease in the U.S. and around the world.
Reference: 1. Wilcox WR, Oliveira JP, Hopkin RJ, Ortiz A, Banikazemi M, Feldt-Rasmussen U, Sims K, Waldek S, Pastores GM, Lee P, Eng CM, Marodi L, Stanford KE, Breunig F, Wanner C, Warnock DG, Lemay RM, Germain DP: Females with Fabry disease frequently have major organ involvement: lessons from the Fabry Registry. Mol Genet Metab 2008, 93:112-128.