Boys with Rett syndrome have 1 of 2 other disorders which allow for a Rett syndrome diagnosis
- Klinefelter syndrome (Also known as 47 or XXY)
- Somatic mosaicism
This is because Rett syndrome is a clinical diagnosis and a clinical diagnosis for boys can only be given if 1 of these conditions is met.
A clinical diagnosis is based on medical signs and patient-reported symptoms, rather than diagnostic tests. It is not a genetic test; genetic tests only confirm mutation/deletion on the MeCP2 gene.
This also means the boys have to present the clinical symptoms that identify Rett from the revised diagnostic criteria table (I have provided a link to the table at the bottom).
Other MeCP2 disorders and encephalopathies
It is possible for boys to have mutations on MeCP2; a prime example of this is MECP2 Duplication (MECP2 is a duplication of the gene rather than a deletion/mutation).
There are also other mutations which are described as MECP2 encephalopathy.
An encephalopathy is a condition that affects the brain.
Having a mutation on MeCP2 is not the same as having Rett syndrome, and it’s very important that we distinguish these differences. Whilst the techniques around treatments might be beneficial to all encephalopathies, they could also be harmful.
It is important, medically, that we understand the differences, and create relevant taxonomies, because the most subtle distinction can have profound affects.
We all share the same wish for all kids, family and friends who live with any form of MeCP2 disorder.
We share the same problems and in many cases the same symptoms. We also share more than that; many “Rett syndrome” organisations are also also a home to the other disorders. While it might technically be different, in our hearts we are family.
This is what we know right now, but facts change, and there’s a chance that something might change. Until then I hope this clarifies why boy with Rett syndrome are so very, incredibly rare.
It’s really important to get the right information out about Rett syndrome.
What new doctors, carers, therapists, teachers and healthcare professionals learn about Rett syndrome, resides on the web. Bad information will result in bad care, and we just cannot afford that.
Klinefelter syndrome (KS) also known as 47,XXY or XXY, is the set of symptoms that result from two or more X chromosomes in males.
Somatic mosaicism happens when the cells of the body are of more than one genotype. Sometimes mosaicism causes intersex conditions, where some cells in the body have XX and other have XY chromosomes
In rare cases, intersex conditions can be caused by mosaicism where some cells in the body have XX and others XY chromosomes
A more common example of an intersex mosaic is 46/47 XY/XXY mosaic or mosaic Klinefelter syndrome. Essentially it means that you have both XY and XXY cells in your body.
Link to the Revised clinical Diagnostic criteria for RTT
If you need clarification, or something doesn’t make sense, please open a chat with me or email me (firstname.lastname@example.org). I will do my best to explain it.
I am not a doctor, or a scientist or a clinician, but I do try take your questions to people that are. I also try run my information past qualified people to ensure it is correct.
If I am wrong, I need to know.