A Midlothian woman has been identified as only one of 12 people in the world to carry a newly discovered genetic mutation linked to the development of a rare and incurable lung disease.

Bailey Lothian, 22, from Bonnyrigg, was diagnosed with Primary ciliary dyskinesia (PCD) aged 10 after years of testing.

The inherited condition - which is estimated to affect approximately one in every 15,000 people in the UK - causes inflammation in the airways which gets worse over time.

It is also associated with complications such as hearing loss and hydrocephalus - a neurological disorder caused by an abnormal build-up of cerebrospinal fluid in the brain.

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To date, scientists had pinpointed mutations in more than 50 genes which could account for 70% of PCD cases, but the remaining third remained a mystery.

A team of researchers from Edinburgh University, led by cell biologist Professor Pleasantine Mill, set out to detect the genetic basis for the other 30% of cases using advanced DNA sequencing techniques. 

A blood sample collected from Bailey was the first to throw up evidence of mutations in a gene called TUBB4B, which had never been seen before. 

This led the scientists to scan samples from other patients around the world who - like Bailey - had been diagnosed with PCD based on symptoms, without a "molecular diagnosis". 

They found another 11 people with the same mutations. 

Bailey's mother, Angela Lothian, said: "Bailey was born on time, but by six weeks old she was really poorly. She ended up in hospital at six weeks old.

"She initially went in with a chest infection but when she got in there they noticed that Bailey's head was larger than normal and she was diagnosed with hydrocephalus.

"It wasn't until she was about two or three years old that they started testing her for PCD, but they always seemed to find it difficult to get any results.

"She had this done about eight times, but it wasn't until she was about 10 or 11 years old that she was eventually diagnosed with PCD."

The Herald: Bailey Lothian, pictured at home in BonnyriggBailey Lothian, pictured at home in Bonnyrigg (Image: Gordon Terris/Herald&Times)

By identifying these extra mutations, genetic screening tests for the condition can be honed to enable more youngsters to get a speedier diagnosis.

While PCD is incurable, earlier detection and treatment can delay PCD from causing permanent lung damage.

The TUBB4B gene is one the building blocks of microtubules - small structures involved in cell shape, movement and cell division, and which are also critical for the formation of cilia, the tiny hairs which clear mucus from the lungs, nose and ears.

When the cilia are unable to work properly - as in patients with PCD - they are more vulnerable to infection and exposure to pollutants.

Some of the mutations in the TUBB4B gene were also associated with vision or hearing loss and kidney disease.

The researchers were able to show that one mutant copy of TUBB4B was capable of over-riding the healthy copy to disrupt microtubule and cilia formation - a phenomenon called the ‘dominant negative’ effect.

This has never previously been observed in PCD.

As well as hydrocephalus, Bailey is deaf in both ears and has breathing difficulties.

None of her three siblings have inherited the condition.

Mrs Lothian, 49, is a full-time carer for her daughter, and hopes that the findings will make it easier for other children who carry the same PCD variant as Bailey to be diagnosed in future.

In addition to improving genetic screening, the discovery is also expected pave the way to better therapies for patients.

Mrs Bailey said: "Bailey has so many things wrong with her that it's been quite hard to link everything.

"It affects her lungs, her head, her ears. She's had a lot to cope with on a daily basis, but to look at Bailey you wouldn't think there's anything wrong with her.

"She looks young for her age and she gets breathless, and she's on IV antibiotics at the moment, but that's just normal for us.

"We've always treated Bailey exactly the same as if she didn't have all these illnesses - even though they do hamper her life.

"It's kind of a relief though [to have that genetic diagnosis]. And it's nice to know that babies being born or young children are going to be easier to diagnose, and that's partly thanks to Bailey."

The Herald: Prof Pleasantine Mill, of Edinburgh University, led the studyProf Pleasantine Mill, of Edinburgh University, led the study (Image: UniversityofEdinburgh)

Prof Mill, chair of cilia biology at Edinburgh University and the group leader at its MRC Human Genetics Unit, said: "This study really highlights how we desperately need to better understand the genetics of PCD and how it relates to patient symptoms and disease progression.

"Not just which gene but how these changes in patient DNA result in disease.

"In this case, it has clear relevance to which of the much-needed therapeutic strategies we need to prioritise for different patients.

"There are many challenges, but also lots of opportunities.

"Our exciting and unexpected insights into rare disease were only possible due to the collaborative partnership between the patients in our studies, their clinicians and researchers with interdisciplinary expertise from across the world.

"We need to continue to build these relationships."