The genetic mutations for Fabry run in families, therefore if a family member has already been diagnosed with Fabry Disease, then diagnosis should be straight forward. Other family members have their levels of α Gal A enzyme checked using an enzyme assay test and/or a genetic test is done to check if they have the same mutation in their DNA. Both the genetic testing, and the enzyme assay test are done by taking blood samples from each individual. The results from the enzyme assay test can take around two weeks to be reported back, but the genetic test results may take several months
If no other family member has Fabry, then it will probably be symptoms that trigger testing. A person may have the pains in the hands and feet, the well documented rash, or perhaps unexplained heart or kidney issues. The test is likely to be a genetic test if the person has no family history of Fabry, although for some males exhibiting classic symptoms (including pains in hands and feet, inability to sweat or the angiokeratoma rash) then an initial blood test to check α Gal A enzyme activity may be taken.
If a male has classic Fabry, then they will have less than 1% α Gal A enzyme found in their blood test. If they have non classic (later onset) Fabry, then they will have some enzyme in the blood test – but at much lower levels than normal.
Females will have very low to normal levels of the α Gal A enzyme in the blood test, depending on how many of their X chromosomes carry the mutated gene.