One of the facts that suggests that it is likely that there are still many more undiagnosed cases of MECP2 Duplication Syndrome than there are diagnosed cases is that geographic, political, and socio-economic factors appear to play important factors in incidence. While some conditions and syndromes are more common in certain gene pools, there is no evidence so far that MECP2 Duplication Syndrome discriminates on the basis of race, geography, or family income.
Nevertheless, it is clear that up until now, the vast majority of cases that have been diagnosed have been found in wealthy nations with highly developed health care systems. Most Eastern European, Asian, South, American countries have reported no cases or only a few cases. The first cases in mainland China were reported only in 2012 in two Han Chinese brothers (Xu et al, 2012: Interestingly, these two boys with long Xq28 duplications including MECP2 were at the mild end of the spectrum. Both could walk, neither had seizures or serious respiratory-infection problems). The Han are probably the largest ethnic group and gene pool on earth, representing more than 93% of mainland China, 98% of Taiwan, and large percentages of the populations of many other countries. If MECP2 Duplication is as common among that group as among North Americans (especially Texans), we might expect 1000s of cases in that group alone.
I single out Texas because when our son was first diagnosed in 2009, I couldn’t help but notice what a large percentage of affected families came from Texas or around Texas. The simple reason was that is where most of the testing was done and that is where doctors were most likely to request testing.
As testing becomes more prevalent, diagnosed cases will also become more prevalent. Currently there are numerous tests done on all newborns in most developed countries. Many of these tests could be replaced by gene Microarrays and as the cost of advanced genetic testing comes down, it is likely that mircoarrays will become standard procedure. When this happens, it will become possible to determine the real incidence of MECP2 Duplication Syndrome. Until that time, a precise estimate will be elusive.
Xu et al. BMC Medical Genetics 2012, 13:75