However, one specific mutation, named R750W , appears to account for a large fraction of Alpha-Mannosidosis disease genes occurring in Turkey, Italy, France, Holland, Germany, Poland, Finland, Sweden, Russia, England, New Zealand, Australia and North America. It was of interest to see if this wide geographic distribution results from recurrent mutational events or whether it results from one single mutation that has spread by migration. By studying specific genetic markers within alpha-mannosidase genes, containing the R750W mutation, we have come to the preliminary conclusion that the R750W mutation results from one, or perhaps two, mutational events that occurred sufficiently long ago to allow this particular mutant gene to spread across Europe by migration. In the last 400-500 years, R750W has spread to the New World by the same mechanisms. This is a common phenomenon called Founder Effect .
Some carriers are of course related directly as siblings or cousins.
It is also reasonable to believe that most R750W carriers have identical alpha-mannosidase genes by descent. There is some uncertainty with regard to the incidence of Alpha-Mannosidosis. The high carrier frequency relates to the fact that the large bulk of recessive disease genes in the population are hidden in normal carriers. Actually, every one of us carries at least several genes for autosomal recessive disorders that would be very damaging and even lethal if homozygous, or expressed. Conclusions There are so many clinical and molecular aspects of Alpha-Mannosidosis that deserve further investigation.