Repeat Expansion Disorders
Disorders such as Fragile X syndrome, Huntingtons Disease, and Myotonic Dystrophy require specialised sequencing. This article details why and how to arrange this service.
Our standard sequencing offering is 30X whole genome sequencing using paired-end short (~150bp-250bp) reads. This is the industry standard for clincal high depth genomics. With this data we can identify the majority of inherited disorders, however some more complex changes require specialised sequencing. Our standard reports will still show for all of the above disorders to help correlate any effects of small variants.
Diseases that are defined by changes in the number of repeating units of a specific sequence are a specific class that require this. These condtions are known as ‘Repeat Expansion Disorders’ and they include the following:
Myotonic Dystrophy
This disorder is caused the following repeat expansions in 100% of all cases:
DM1: DMPK CTG
DM2: CNBP CCTG
Fragile X
This disorder is caused by the following repeat expansions in more than 99% of all cases:
FMR1 CGG
Huntington
This disorder is caused by the following repeat expansions in 100% of all cases:
HTT CAG
Additionally, some disorders are sometimes caused by the same mechanism:
Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD)
This disorder is caused by the following repeat expansions in ~40% of all cases of ALS and in ~50% cases of FTD.
C9orf72 G4C2
This list is not exhaustive and we would recommend getting in touch with us before placing an order if you would like to know whether a specific condition is not identifiable with our short reads offering.
If you have a specific concern about these disorders in particular we would recommend contacting us to organise long read sequencing. This is a service we can offer in addition to our short read offering at an additional cost.