The team, from the Centre for Genomic Medicine at The University of Manchester, have developed a test that checks all genes known to cause congenital cataracts using just one blood sample.
“Using next-generation sequencing, we are now able to identify the cause of cataracts in children in a way that is much faster and more cost-effective than the current method,” said Rachel Gillespie, who developed the test and spoke at speaking at the recent British Genetic Medicine conference.
Congenital cataracts are a leading cause of blindness in children, affecting around 200,000 children around the world every year. It is thought around half of cases are due to genetic mutations whilst the remainder are caused by environmental risk factors during pregnancy, for example exposure to infections such as rubella.
Mutations in over 100 genes have been linked to congenital cataracts. Conventional screening methods involve the consecutive testing of each gene separately to determine the precise genetic cause, which is a time-consuming and costly process.
“At the moment, screening for one gene takes around four weeks. There are more than 100 known genes linked to congenital cataracts, so establishing the cause by screening genes individually can sometimes take years,” said Gillespie. “Our test looks at all of these genes in parallel, so patients can be diagnosed much faster and receive the treatment, clinical management and genetic counselling they need.”
As more patients are tested and more knowledge is gained about the genetic basis of the condition, it is hoped that pinpointing the exact mutation responsible will enable doctors to make more accurate predictions regarding how the cataracts may progress and what the outcome of surgery may be.
Genetic testing can also bring to light more complex conditions whose symptoms typically do not emerge until later in life. “In some cases, we have identified that the cataracts aren’t just a standalone problem, but a symptom of a more complex syndrome,” said Gillespie. “This includes Warburg micro syndrome and galactokinase deficiency, both rare conditions that are probably under-diagnosed, as warning signs in children can be subtle.”
The team, from The University of Manchester and the Central Manchester NHS Foundation Trust, are validating the test and it will become available on the NHS by December this year, from which point they will be accepting samples for diagnostic testing. The team consists of Professor Chris Lloyd from Manchester Royal Eye Hospital, Professor Graeme Black and Professor Jill Clayton-Smith St Mary’s Hospital and University of Manchester Institute of Human Development and Rachel Gillespie, University of Manchester.
The research was funded by Fight for Sight.
Notes for editors
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