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The gene in question, FLCN, is linked to a condition known as , symptoms of which include benign skin tumours, lung cysts, and an increased risk of kidney cancer.

In a study , a team from the University of Cambridge examined data from , the , and East London Genes & Health – three large genomic datasets encompassing more than 550,000 people.

They discovered that between one in 2,710 and one in 4,190 individuals carries the particular variant of FLCN that underlies Birt-Hogg-Dubé syndrome. But curiously, whereas patients with a diagnosis of Birt-Hogg-Dubé syndrome have a lifetime risk of collapsed lung of 37%, in the wider cohort of carriers of the genetic mutation this was lower at 28%. Even more striking, while patients with Birt-Hogg-Dubé syndrome have a 32% of developing kidney cancer, in the wider cohort this was only 1%.

Collapsed lung – known as pneumothorax – is caused by an air leak in the lung, resulting in painful lung deflation and shortness of breath. Not every case of collapsed lung is caused by a fault in the FLCN gene, however. Around one in 200 tall, thin young men in their teens or early twenties will experience a collapsed lung, and for many of them the condition will resolve itself, or doctors will remove air or fluid from their lungs while treating the individual as an outpatient; many will not even know they have the condition.

If an individual experiences a collapsed lung and doesn’t fit the common characteristics – for example, if they are in their forties – doctors will look for tell-tale cysts in the lower lungs, visible on an MRI scan. If these are present, then the individual is likely to have Birt-Hogg-Dubé syndrome.

Professor Marciniak is an honorary consultant at ��ѻ��ý ��ѻ��ý Foundation Trust and Royal Papworth Hospital ��ѻ��ý Foundation Trust and a researcher at the University of Cambridge. He co-leads the ��ѻ��ý Familial Pneumothorax Rare Disease Collaborative Network, together with Professor Kevin Blyth at Queen Elizabeth University Hospital and University of Glasgow. The aim of the Network is to optimise the care and treatment of patients with rare, inherited forms of familial pneumothorax, and to support research into this condition.

Professor Marciniak says he was surprised to discover that the risk of kidney cancer was so much lower in carriers of the faulty FLCN gene who have not been diagnosed with Birt-Hogg-Dubé syndrome.

The finding raises the question of whether, if an individual is found to have a fault FLCN gene, they should be offered screening for kidney cancer. However, Professor Marciniak does not believe this will be necessary.

“With increasing use of genetic testing, we will undoubtedly find more people with these mutations,” he said, “but unless we see the other tell-tale signs of Birt-Hogg-Dubé syndrome, our study shows there's no reason to believe they’ll have the same elevated cancer risk.”

The research was funded by the , with additional support from the National Institute for Health and Care Research Cambridge Biomedical Research Centre.