Although MECP2 Duplication Syndrome (or Xq28 Duplication) is correctly identified as a rare condition, available research suggests that it is not as rare as we once thought. For example, Japanese researchers published a 2014 study in Human Genome Variation that described from results of 1,250 patients with intellectual disabilities who had not received specific diagnoses. The researchers performed advance genetic testing on these 1,250 patients and found probable genetic causes for 17% of these individuals. Many different genetic conditions were found among these 17% of patients. However, one condition was found more frequently than any other. That condition was Xq28 duplication with duplication of the MECP2 gene. This suggests that MECP2 Duplication Syndrome is not nearly as rare as once believed and that many cases continue to go diagnosed.
In the words of the researchers:
Duplications of the Xq28 region are the most frequent chromosomal aberrations observed in patients with intellectual disability (ID), especially in males.
Among the identified aberrations, the most frequently observed copy number gain was the Xq28 duplication.
This suggests that MECP2 Duplication Syndrome is not so much an exceptionally rare disorder as it is an under-diagnosed disorder. In advocating for services and funding for research, this distinction may be important. Asking for support to help a very small number of individuals may be more difficult to justify than making the case for a much larger number of individuals who may be affected.
LINK TO ARTICLE: Clinical impacts of genomic copy number gains at Xq28. Human Genome Variation. Toshiyuki Yamamoto, Keiko Shimojima, Shino Shimada, Kenji Yokochi, Shinsaku Yoshitomi, Keiko Yanagihara, Katsumi Imai & Nobuhiko Okamoto