A baffling eye infection that had plagued a British doctor for five years was finally identified after a breakthrough test identified it and helped save her eyesight.
Ellie Irwin (29) had suffered the mystery inflammation in her right eye for years, which resulted in blurred vision. No treatment helped and at one point she even considered having her eye removed.
It was only after she was offered a “last resort” analysis called metagenomics that she was diagnosed with a rare bacterial infection, which was cured with antibiotics.
It is now presumed she picked up the bug swimming in the Amazon river in 2018, on a trip to South America.
She told the BBC the lifesaving diagnosis had been “transformative”.
Professor Carlos Pavesio, consultant ophthalmologist at Moorfields Eye Hospital in London, described her case as a “breakthrough in the diagnosis of infectious diseases”.
“There are many patients we treat with chronic infections for years, but despite multiple tests we cannot always identify the bug responsible,” he said.
The inflammation had first affected Irwin’s right eye in 2019, when she was still at medical school. All tests for infection came back negative and it was assumed she had an autoimmune condition.
She was prescribed steroid eye drops and immunosuppressants, some of which needed to be given by intravenous infusion.
“It was completely dominating my life,” she said. “I needed eye drops every single hour and it was difficult to balance that alongside starting work as a junior doctor. My vision was really variable, and I would have some bad days.
“I was on so much medication and going to so many appointments, yet I didn’t feel as if I were getting any better.”
The treatment and inflammation led to her developing a cataract that had to be surgically removed, just after she graduated from medical school.
She eventually reached “breaking point”, and even began considering having her affected eye removed.
“While losing sight in one eye is terrifying,” she said, “my biggest fear was that it might spread to my left eye.”
One of her doctors at Southmead Hospital in Bristol suggested metagenomics – a last resort test not generally available to patients and only used where standard diagnostic tools have failed to identify or rule out infection.
Metagenomics technology uses cutting-edge genomic sequencing, which can identify all bacteria, fungi or parasites present in a sample by comparing them against a database of millions of pathogens.
A team at Moorfields Eye Hospital arranged for a sample of fluid to be taken from inside her eye and sent to the metagenomics labs at Great Ormond Street Hospital (GOSH) – the only lab in the UK officially recognised to carry out these diagnostic tests for patients, and one of only a few in the world.
Currently, the standard method for detecting bacterial infections is by trying to grow a sample of it in a Petri dish.
For viruses, the most common diagnostic tool is a PCR test, Dr Julianne Brown, principal clinical scientist at the GOSH metagenomics service, said PCR has some drawbacks.
“The trouble with PCR is that you have to think of the viruses that might be causing an infection and do a separate test for each one,” she said. “So if you’ve got an infection with something that’s unexpected, rare or not previously known, you won’t find it.”
Brown described metagenomics as “an enormous step up … it’s a complete game-changer”.
In Irwin’s case, metagenomics diagnosed a rare strain of the bacterial infection leptospirosis found in South America.
It is now presumed she picked up the bug swimming in the Amazon river in 2018, while on a trip to Ecuador and Colombia.
She said it was an emotional moment when she was given the results of the test.
“I broke down – I just had to cry. I never imagined that it would come back positive and be for something that was treatable,” she said.
“I was given three weeks of antibiotics and within days, my vision was clearer and the inflammation subsided.”
A single metagenomics test costs around £1 300, which is far more than standard diagnostics. However, as the technology is developed that price is likely to fall rapidly.
Virologist Professor Judy Breuer, who has been developing metagenomics at GOSH and University College London (UCL) for more than a decade, said her team currently receives three or four samples a week from hospitals around the UK for metagenomic testing, in addition to those it carries out on its own patients.
These are often samples from parts of the body that are normally sterile sites, where bacteria are not usually found – such as the brain, central nervous system, liver and eye.
“In the future, we think metagenomics will become a first line test and be able to diagnose infection in any sample, probably within the same day,” she said.
It’s also likely to become faster, cheaper and easier to do, meaning it will become available to more patients rather than just a small number who are severely unwell.
BBC article – Woman’s eyesight saved by cutting-edge test after mystery infection (Open access)
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