The population of "People who know" indicated here is an estimate of the number of individuals in the U.S. that know they carry the Fabry gene. It is not a validated number from any official source. The estimate is derived from many sources to include the number of individuals who register on the NFDF website and acknowledge themselves as carrying the hereditary gene and an estimate from Fabry registry data.  As you can see by the number of estimated cases in the U.S. compared to the estimated number of people who carry the Fabry gene is very low, about 5%. The majority of affected people do not know they have the Fabry gene and are vulnerable to the severe impacts of this disease without knowing the cause or remedy.