When an otherwise healthy middle-aged man suddenly began experiencing intense fatigue, malaise, and increasing difficulty breathing, his doctors were stumped. Four inconclusive visits with his general practitioner provided little resolve, and it was only a matter of time before the 43-year-old would exhibit symptoms so severe that his daily life was affected.

Doctors initially attributed the mystery condition to a lower respiratory tract infection. A chest radiograph indicated his respiratory health was otherwise “normal”, but symptoms were becoming so bad that he could only stand or walk for a few minutes without feeling like he was going to pass out. 

“Two months after the onset of the symptoms, I was unable to stand or walk for more than a few minutes at a time without feeling like I was going to pass out,” wrote the patient in the case study. “Going upstairs to bed was a 30min activity as I could only manage two stairs at a time and then needed to sit and rest. I was signed off work and spent most of the time asleep (day and night).”

A team of doctors began to look at other potential contributors. A blood test revealed that the patient had antibodies present to bird feather dust, but although the man admitted to having a small amount of mold in his bathroom and owning a cat and dog, he said he had no birds. X-rays indicated that the man had hypersensitivity pneumonitis, a condition where the air sacs and airways become inflamed due to a triggered immune response, typically by repeatedly inhaling allergens that can sometimes result in irreversible damage. That’s when he remembered that he and his wife had recently replaced their synthetic bedding with a feather-filled duvet.

The diagnosis: feather duvet lung (FDL), or extrinsic allergic alveolitis, resulting from the repeated inhalation of organic dust from duck or goose feathers found in duvets and pillows.

Doctors advised the man to get rid of his feather-filled bedding immediately, as well as to clean out the bathroom mold and make sure no birds were roosting in his attic. He was also prescribed a series of steroids. Within the first month, his symptoms “improved rapidly” and disappeared entirely within a year.

"[FDL] is not unique – other cases have been described – but just highlights the importance of asking about exposures when taking a history," report author Dr Owen Dempsey, from the National Health Service, told IFLScience. "It is a very satisfying diagnosis to make, both for the clinician (makes us feel smart!) and the patient (removing the duvet is a pretty easy treatment!)."

FDL is a condition that is difficult to diagnose as symptoms can range from fatigue to flu-like symptoms. As the report authors note, this is only one case and it is unknown how common it might be. Doctors often miss it because they don’t ask about feather bedding. Due to the broad range of symptoms, researchers note it is likely many cases of FDL are either missed or diagnosed late.

“Our case reinforces the importance of taking a meticulous exposure history and asking about domestic bedding in patients with unexplained breathlessness,” write the authors in BMJ Case Reports. “Prompt recognition and cessation of antigen exposure may prevent the development of irreversible lung fibrosis."

The man says that his oxygen saturation levels have since returned to normal and he has not had any “dizzy turns” since recovering.

“It doesn’t affect me at all now and my life is pretty much as it was before,” he adds.

But don't go tossing out your feather-filled duvets just yet. 

"Most folk will be absolutely fine. So, mass binning of duvets and pillows is not the key message, rather just that patients and their health care professionals should be meticulous in their history taking and mindful of existing and perhaps novel exposures, yet to be discovered," said Dempsey.